new research on vaccines

This article is outdated. For information about the updated 2024-2025 COVID vaccines, click here .

[Originally published: Oct. 2, 2023. Updated: April 19, 2024.]

Note: Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

There has been better protection against severe disease, hospitalization, and death from COVID-19 since newly updated (2023–2024 formula) mRNA COVID vaccines became available last fall. Shots are available to protect everyone 6 months and older from serious illness, hospitalization, and death from the disease.

The Food and Drug Administration (FDA) authorized the updated vaccines by Pfizer-BioNTech and Moderna for infants and children ages 6 months to 11 years, and approved them for everyone ages 11 years and older. It also authorized an updated Novavax vaccine for those 12 and older in the fall of 2023.

The vaccines target XBB.1.5, a subvariant of Omicron that dominated the United States—and the world—from November 2021 until last year. The CDC says the updated vaccines should also work against currently circulating variants of the SARS-CoV-2 virus—many of which descended from, or are related to, the XBB strain. The vaccine is also expected to protect against JN.1, the current dominant strain in the U.S.

While COVID has been causing mostly mild illness recently, Yale Medicine infectious diseases specialist Onyema Ogbuagu, MBBCh , reminds people that the disease can still lead to hospitalization and death. “Infections can have long-term consequences,” Dr. Ogbuagu says, adding that even healthy people can develop Long COVID —a condition in which new, continuing, or recurring (and sometimes debilitating) symptoms are present four or more weeks after an initial coronavirus infection.

Below, Yale experts tell you what you need to know about the updated COVID vaccine.

1. Why would another COVID vaccination help?

The updated vaccines are not expected to prevent all cases of COVID, including those causing mild illness; rather, their aim is to reduce severe illness, hospitalization, and death from infection. According to the CDC, COVID is still a major cause of serious respiratory illness. While hospitalizations and deaths from COVID have been declining, 7,318 people were hospitalized with the disease during the first week of April 2024 alone (that number rose as high as 35,000 during one week in January, a month when respiratory diseases tend to peak).

Older people (especially those ages 50 and older) are more likely than younger people to get very sick from COVID. Immunocompromised people and those with chronic medical conditions, such as diabetes or heart disease, are at the highest risk of severe disease and death, but some young, healthy people have also gotten very ill and died from COVID. In addition, the CDC recommends the vaccine for pregnant women to protect both mother and baby.

An analysis by the CDC in September 2023 suggested that making its vaccine recommendation universal could prevent 400,000 hospitalizations and 40,000 deaths in the U.S. over the next two years.

2. How is the updated COVID vaccine different from the previous one?

The bivalent booster, which is no longer available, was introduced in the fall of 2022. It targeted the BA.4 and BA.5 Omicron subvariants and the original SARS-CoV-2 virus. The updated vaccine is monovalent, designed to prevent severe disease from the Omicron XBB.1.5 subvariant. By September 2023, the long-running XBB.1.5 accounted for only about 3% of cases in the U.S., but most of the strains circulating now are descended from (or closely related to) it.

That’s a good example of how the virus has evolved—and it’s still evolving—so rapidly that it may be impossible to match each new vaccine update to the variants circulating at the time it is released, explains Scott Roberts, MD , a Yale Medicine infectious diseases specialist. “But we know from experience that the vaccines hold up very well, even against multiple variants, unless there is a significant shift like we saw with Delta to Omicron in the winter of 2021,” he says. “Basically, if you have some immunity to a variant and are exposed to a new offshoot of it, you’ll have some protection.”

3. Why isn’t the new COVID vaccine considered a booster?

The FDA is calling the newest shots “updated vaccines” in anticipation of needing to provide updated formulas annually, similar to the flu shot, which changes each year.

A booster shot gives a “boost” to the recipient's existing immunity from a previous vaccination. Updated vaccines are different in that they are expected to provide protection against currently circulating variants, helping the body build a new response to those variants. “Barring the emergence of a markedly more virulent variant, the FDA anticipates that the composition of COVID vaccines may need to be updated annually, as is done for the seasonal influenza vaccine,” the FDA noted in its approval and authorization of the new vaccine.

“I think we're going to fall into a pattern very similar to the flu, where every year the virus is going to mutate slightly, and the vaccine formulation for the fall will be an educated guess,” says Dr. Roberts. “We will make a vaccine targeted against whatever we predict or whatever is currently circulating and hope our vaccines are a good match, because we will be developing them before we know what variants will be circulating in the fall."

4. How safe is the updated COVID vaccine?

COVID vaccines are safe and effective, according to the CDC . The safety of COVID vaccines has been rigorously monitored and evaluated since their emergency use authorization (EUA) in December 2020. According to the CDC, the updated mRNA COVID vaccines for 2023-2024 are manufactured using a similar process to the previous vaccines.

The benefits of the COVID vaccine continue to outweigh any potential risks, and serious reactions after COVID vaccination are rare, according to the CDC. The agency cited a study showing the risk of cardiac complications, including myocarditis (an inflammation of the heart muscle) was significantly higher after a COVID infection for both males and females in all age groups.

5. Are there any special COVID vaccine recommendations for children?

The FDA approved the updated mRNA vaccines for adolescents and teenagers ages 12 and older and authorized them for emergency use in children ages 6 months through 11 years.

Children are less likely to get seriously ill with COVID, but some still do, says Magna Dias, MD , a Yale Medicine pediatric hospitalist. She tells parents who are still not sure whether they should get the vaccine for their children to talk to their pediatrician, especially if their child is immunocompromised. “In that case, I think it’s a no-brainer to protect them,” she says.

6. Is there an updated COVID vaccine from Novavax?

The FDA authorized an updated version of a vaccine Novavax developed to target the XBB.1.5 strain. Individuals 12 and older previously vaccinated with a COVID vaccine (and who have not already been vaccinated with a recently updated mRNA COVID vaccine) are eligible to receive one dose; unvaccinated individuals can receive two doses.

According to the FDA , the updated vaccine addresses currently circulating variants to provide better protection against serious consequences of COVID, including hospitalization and death.

The Pfizer-BioNTech and Moderna vaccines use messenger RNA (mRNA) technology, which instructs the body’s cells to make proteins that trigger an immune response against COVID. The Novavax protein-based vaccine uses an older, more traditional technology and a different mechanism—it directly injects the spike protein (formulated in a laboratory) and another ingredient into the body, leading to the production of virus-fighting antibodies and T cells. The Novavax vaccine is the only non-mRNA COVID vaccine available in the U.S.

7. When should I get the updated COVID vaccine?

People 5 years and older may get one dose of the updated vaccine at least two months after the last dose of any previous COVID vaccine. Babies and young children usually need more doses than older children and teens. Anyone who recently had COVID may consider delaying their vaccine by 3 months.

People who are 65 or older should receive their second dose of the updated vaccine at least four months after the first dose. Those in that age group who are immunocompromised should get the additional dose earlier—at least 2 months after the first one.

8. Should I get the updated COVID vaccine and other seasonal shots at the same time?

The CDC considers it safe to get the COVID shot and annual flu vaccine simultaneously. There is even research in progress to explore the effects of administering both vaccines in a single shot.

But the respiratory syncytial virus (RSV) vaccines for older adults and pregnant women (who can pass the antibodies along to their newborns) were brand new in fall 2023, and there isn’t data to say for sure whether giving those at the same time as the other two shots is the best strategy.

9. Where can I get the updated COVID vaccine?

As with previous COVID vaccines, this one will be available at participating pharmacies and provider offices. To find a location near you that carries the vaccine and to schedule an appointment, go to Vaccines.gov . You can also call 1-800-232-0233 (TTY 1-888-720-7489). Be aware that current distribution and insurance issues may delay availability of the vaccines temporarily in some places.

According to the CDC, the vaccines are covered by insurance, including private insurance, Medicare plans, and Medicaid plans. Uninsured children and uninsured adults also have access through the Vaccine for Children Program and Bridge Access Program , respectively.

Information provided in Yale Medicine articles is for general informational purposes only. No content in the articles should ever be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider with any questions you have regarding a medical condition.

More news from Yale Medicine

Study Largely Confirms Known, Rare COVID-19 Vaccine Side Effects

By Kate Yandell

Posted on February 27, 2024

SciCheck Digest

An international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects.

More than  half a billion doses of COVID-19 vaccines have now been administered in the U.S. and only a few, very rare, safety concerns have emerged. The vast majority of people experience only minor, temporary side effects such as pain at the injection site, fatigue, headache, or muscle pain — or no side effects at all. As the Centers for Disease Control and Prevention has said , these vaccines “have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.”

A small number of severe allergic reactions known as anaphylaxis, which are expected with any vaccine, have occurred with the authorized and approved COVID-19 vaccines. Fortunately, these reactions are rare, typically occur within minutes of inoculation and can be treated. Approximately 5 per million people vaccinated have experienced anaphylaxis after a COVID-19 vaccine, according  to the CDC.

To make sure serious allergic reactions can be identified and treated, all people receiving a vaccine should be observed for 15 minutes after getting a shot, and anyone who has experienced anaphylaxis or had any kind of immediate allergic reaction to any vaccine or injection in the past should be monitored for a half hour. People who have had a serious allergic reaction to a previous dose or one of the vaccine ingredients should not be immunized. Also, those who shouldn’t receive one type of COVID-19 vaccine should be monitored for 30 minutes after receiving a different type of vaccine.

There is evidence that the Pfizer/BioNTech and Moderna mRNA vaccines may rarely cause inflammation of the heart muscle (myocarditis) or of the surrounding lining (pericarditis), particularly in male adolescents and young adults .

Based on data collected through August 2021, the reporting rates of either condition in the U.S. are highest in males 16 to 17 years old after the second dose (105.9 cases per million doses of the Pfizer/BioNTech vaccine), followed by 12- to 15-year-old males (70.7 cases per million). The rate for 18- to 24-year-old males was 52.4 cases and 56.3 cases per million doses of Pfizer/BioNTech and Moderna vaccines, respectively.

Health officials have emphasized that vaccine-related myocarditis and pericarditis cases are rare and the benefits of vaccination still outweigh the risks. Early evidence suggests these myocarditis cases are less severe than typical ones. The CDC has also noted that most patients who were treated “responded well to medicine and rest and felt better quickly.”

The Johnson & Johnson vaccine has been linked to an  increased risk of rare blood clots combined with low levels of blood platelets, especially in women ages 30 to 49 . Early symptoms of the condition, which is known as thrombosis with thrombocytopenia syndrome, or TTS, can appear as late as three weeks after vaccination and  include  severe or persistent headaches or blurred vision, leg swelling, and easy bruising or tiny blood spots under the skin outside of the injection site.

According to the CDC, TTS has occurred in around 4 people per million doses administered. As of early April ,  the syndrome has been confirmed in 60 cases, including nine deaths, after more than 18.6 million doses of the J&J vaccine. Although TTS remains rare, because of the availability of mRNA vaccines, which are not associated with this serious side effect, the FDA on May 5 limited authorized use of the J&J vaccine to adults who either couldn’t get one of the other authorized or approved COVID-19 vaccines because of medical or access reasons, or only wanted a J&J vaccine for protection against the disease. Several months earlier, on Dec. 16, 2021 ,  the CDC had recommended the Pfizer/BioNTech and Moderna shots over J&J’s.

The J&J vaccine has also been linked to an increased risk of Guillain-Barré Syndrome, a rare disorder in which the immune system attacks nerve cells.  Most people  who develop GBS fully recover, although some have permanent nerve damage and the condition can be fatal.

Safety surveillance data suggest that compared with the mRNA vaccines, which have not been linked to GBS, the J&J vaccine is associated with 15.5 additional GBS cases per million doses of vaccine in the three weeks following vaccination. Most reported cases following J&J vaccination have occurred in men 50 years old and older.

Link to this

COVID-19 vaccines — like all  vaccines  and other medical products — come with side effects, including  serious side effects  in rare cases. The vaccines were rolled out to protect people from a novel virus that has  killed  millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from experts and governmental health agencies that the benefits of COVID-19 vaccination outweigh the risks.

Researchers have  scrutinized  the COVID-19 vaccines’ safety and continue to do so. A  study  published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer/BioNTech and Moderna vaccines, which have been  widely given  in the U.S., as well as the AstraZeneca vaccine, which was  never authorized  in the U.S.

“What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author  Anders Hviid , head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.”

Many popular posts on social media have shared results from the study, some lacking the context that the identified  health problems are rare , that most aren’t new and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people should not have received the vaccines , that the risks outweigh the benefits or that the  risk of the rare side effects is greater than was reported in the study.

“Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular  post , referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post  article  about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.”

“This thing was forced on people who faced almost no risk from Covid,” said another widely read post . “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose.

The Vaccine study confirmed that the Moderna and Pfizer/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions involving inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was  identified via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the  CDC says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest.

The study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these  problems  were  linked  to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available.

The study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune condition that causes inflammation of the brain and spinal cord.

Hviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer/BioNTech vaccine which has been more widely used,” he said.

“We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.”

Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare

The Vaccine  study  drew on national or regional health records from eight countries with institutions participating in the  Global Vaccine Data Network , an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine. 

The researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination.

“This study confirms the primary already detected and validated side effects established by previous literature,”  Jeffrey S. Morris , director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines. 

Morris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.” 

ADEM  involves  inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a  sudden onset  and typically eventually improves, with a full recovery in many, although not all, cases.

After the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine. 

The data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.”

The authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological  events  have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination.

The study means that “early warning systems are solid,” said  Marc Veldhoen , an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a  post  on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.”

Identifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients.

Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation.

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TheBlaze. “ Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture .” Facebook. 20 Feb 2024.

Dr. Anthony G. Jay (@anthonygjay). “ I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐 .” Instagram. 20 Feb 2024.

bikinibottom_fish 🐟 (@bikinibottom_fish). “ Global Study Links COVID-19 Vaccines to Heart and Brain Issues! ” Instagram. 20 Feb 2024.

PatrioticBabe 🇺🇸 (@babedoesthenews). “ ❗️ .” Instagram. 20 Feb 2024.

RASPY RAWLS (@raspy_rawls2). “ … We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …  .” Instagram. 20 Feb 2024.

Jaimee Michell (@thegaywhostrayed). “ I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW! ” Instagram. 20 Feb 2024.

Liberty Counsel (@libertycounsel). “ …  “Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” … ” Instagram. 20 Feb 2024.

Shemeka Michelle (@ theshemekamichelle ). “ Remember when they called them “rare” breakthrough cases? Yeah, me too. #slight .” Instagram. 20 Feb 2024.

Mal’aki (@awake.the.mind). “ ‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists .” Instagram. 20 Feb 2024.

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COVID-19 vaccines effective in reducing long COVID symptoms

• 16 January 2024

A study funded by the NIHR has found that vaccination against COVID-19 consistently reduced the risk of long COVID symptoms.

Researchers from the University of Oxford and Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences (NDORMS) examined data from more than 20 million people. The individuals came from the UK, Spain and Estonia. Some had been vaccinated and others had not. 

People were defined as having long COVID if they had:

• experienced at least one of 25 WHO-listed symptoms
• experienced the symptoms between 90 and 365 days after the date of a positive PCR test or clinical diagnosis of COVID-19
• no history of that symptom 180 days before they were infected with COVID-19

The research team observed a significant decrease in the occurrence of long COVID among vaccinated individuals. This was in comparison to those who were unvaccinated. The findings were consistent across all three European countries and four databases, covering different healthcare settings and national healthcare policies.

The research has been published in The Lancet Respiratory Medicine . The team was supported by the NIHR Oxford Biomedical Research Centre (BRC).

Protection from long COVID

Dani Prieto-Alhambra, Professor of Pharmaco- and Device Epidemiology at NDORMS and an NIHR Senior Research Investigator , led the study. He said: “Vaccines proved to be highly effective in preventing severe COVID-19 but it’s known that around 1 in 10 people suffer from persistent symptoms, what we call long COVID. We wanted to assess if COVID vaccines had any impact on long COVID symptoms.”

Dr Annika Jodicke, Senior Pharmacoepidemiologist and study co-lead, said: “We were able to demonstrate how the vaccines prevented the development of persistent COVID symptoms. Additionally, we compared different vaccinations and found that the BNT162b2 vaccine (BioNTech/Pfizer) provided better protection against long COVID compared to the ChAdOx1 vaccine (Oxford/AstraZeneca).”

The study was funded by the NIHR through a call to research long COVID prevention and treatment. The NIHR awarded £19.6m to 15 projects across England in 2021 to explore causes of long COVID, symptoms and treatments.

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• CORONAVIRUS COVERAGE

Here’s the latest on COVID-19 vaccines

Everything you need to know about the COVID-19 vaccines—from their safety and efficacy to the global vaccine rollout.

Editor’s note: As of November 2021, this COVID-19 vaccine tracker is no longer being updated. Stay up-to-date on the latest vaccine developments and other COVID-19 news here .

COVID-19 vaccines have reached consumers in record time. Though the process can typically take 10 to 15 years , the U.S. Food and Drug Administration has granted emergency authorization to vaccines made by Pfizer, Moderna, and Johnson & Johnson in less than a year. Before now, the fastest-ever vaccine—for mumps— took four years to develop in the 1960s.

Fortunately, scientists had started working on the seeds of these vaccines long before COVID-19 emerged–teams were doing breakthrough work on mRNA technology for 12 years before the pandemic, and a global push to make clinical trials for COVID-19 more efficient helped ensure the world had safe, effective drugs in record time.

Even after a vaccine is authorized or fully licensed, it faces potential roadblocks when it comes to scaling up production and distribution, which also includes deciding which populations should get it first —and at what cost.

Here’s everything you need to know—including primers on how vaccines and clinical trials work, the latest news on vaccine distribution and safety, and a detailed breakdown of the early candidates.

Vaccines and clinical trials

Vaccines go through a three-stage clinical trial process that’s required before they are sent to regulatory agencies for approval. Given the urgent need, some vaccine developers compressed the clinical process for SARS-CoV-2 by running trial phases simultaneously.

VACCINE CLINICAL TRIAL PROCESS

Phase one: Checks the safety of a vaccine and determines whether it triggers an immune response in a small group of healthy humans. 

Phase two: Widens the testing pool to include groups of people who may have the disease or be more likely to catch it, to gauge the vaccine’s effectiveness. 

Phase three: Expands the pool up to the thousands to make sure the vaccine is safe and effective among a wider array of people, given that immune response can vary by age, ethnicity, or by underlying health conditions.

The COVID-19 candidates, like all vaccines, essentially aim to instruct the immune system to mount a defense, which is sometimes stronger than what would be provided through natural infection and comes with fewer health consequences .

To do so, traditional vaccines use the whole coronavirus, but in a killed or weakened state. Others use only part of the virus—whether a protein or a fragment. Some transfer the instructions for coronavirus proteins into an unrelated virus that is unlikely or even incapable of causing disease. Finally, cutting-edge vaccines under development rely on deploying pieces of the coronavirus’s genetic material, enabling our cells to temporarily make coronavirus proteins needed to stimulate our immune systems. ( Find out more about vaccines and how they work .)

TYPES OF VACCINES

Nucleic acid: Relies on injecting snippets of a virus’s genetic material, either DNA or messenger RNA (mRNA), into human cells. It spurs the production of viral proteins that mimic features of the coronavirus, training the immune system to recognize its presence. 

Knocked-out virus: Uses a non-infectious form of the coronavirus that can no longer cause full-blown disease but can still provoke an immune response. The virus can either be fully inactivated or weakened. These modes are considered the most classic ways to make vaccines.

Viral vector: Essentially a “Trojan horse” presented to the immune system. One type involves introducing a piece of DNA from SARS-CoV-2 into another unrelated germ—for example, an adenovirus, which typically causes the common cold. When this modified adenovirus is injected into humans, the hope is that it will instruct cells to make coronavirus proteins and will trigger an immune response.

Protein: These vaccines are typically made from coronavirus proteins, which can be synthesized or brewed in labs like beer. Some versions involve coating a carrier—such as nanoparticles—with proteins to better aid delivery and uptake by cells.

U.S. vaccine rollout

Three COVID-19 vaccines are available for use in the United States. U.S. regulators have approved Pfizer’s vaccine for adults and authorized it for emergency use in children and adolescents ages five to 17. The U.S. has also granted emergency use authorization to administer the Moderna and Johnson & Johnson vaccines to adults.

Some populations in the country are eligible for booster doses. Anyone who received a Johnson & Johnson single-shot jab can get a second dose after at least two months. People who received the Pfizer and Moderna vaccines are eligible for a third dose after six months if they are over 65 or have an underlying condition that makes them more susceptible to severe COVID-19. People whose institutional or occupational settings put them at high risk of exposure to the coronavirus may also get a booster shot. U.S. regulators have permitted people to mix-and-match their jabs in the wake of data suggesting that people who originally received the Johnson & Johnson vaccine are protected by a booster dose of the Pfizer or Moderna vaccines.

U.S. regulators have also recommended a third dose of the Pfizer and Moderna vaccines for people with compromised immune systems. This extra dose is considered part of their primary vaccination series; CDC guidance suggests that immunocompromised people will be able to get a fourth booster dose six months after completing the primary series.

Global vaccine rollout

The World Health Organization is coordinating global efforts to administer vaccines, with an eye toward delivering two billion doses by the end of 2021. It is leading an initiative through the COVAX Facility to ensure that all countries have equitable access. The WHO has approved the Pfizer-BioNTech, AstraZeneca-Oxford, Johnson & Johnson, Moderna, Sinopharm, Sinovac, and Bharat Biotech vaccines for emergency use.

Vaccine safety

On July 13, the U.S. Food and Drug Administration added a warning label to Johnson & Johnson’s vaccine after it was linked to rare cases of Guillain-Barré Syndrome, an autoimmune disorder that can lead to paralysis. There have been 100 preliminary reports of the syndrome among the approximately 12.5 million people who have received the vaccine. The FDA said that the benefits of receiving the vaccine outweigh the risks.

The FDA has also added a warning label to the Pfizer and Moderna vaccines about rare cases of heart inflammation in adolescents and young adults. The move came after the CDC’s Advisory Committee on Immunization Practices announced that it has identified more than 300 cases of myocarditis and pericarditis that it acknowledged are likely linked to the vaccines. The agency says these cases are rare but higher than expected. It also said the benefits of the shots outweigh the risks.

  In April, the European Medicines Agency issued statements saying that unusual blood clots should be listed as a very rare but possible side effect of both the AstraZeneca and Johnson & Johnson vaccines. In a review of 86 reported cases related to the AstraZeneca vaccine, the EMA’s safety committee found a potential link between it and the clots, with most known cases occurring in women under age 60 within two weeks of receiving the first dose. The EMA stressed that the odds of developing a clot after vaccination are extremely low, and that the benefits of getting vaccinated outweigh the risks. They also recommend that people seek immediate medical attention if they experience symptoms related to clotting, including persistent pain, shortness of breath, and headaches or blurred vision.

On August 27, a study published in the British Medical Journal affirmed the EMA’s risk-benefit analysis, showing that there’s a much higher risk of developing blood clots after SARS-CoV-2 infection than after immunization with the AstraZeneca or Pfizer vaccines.

On August 11, the CDC officially recommended that people who are pregnant, breastfeeding, or may become pregnant get a COVID-19 vaccine . A new analysis of data from the vaccine rollout found no increased risk of miscarriage among people who received an mRNA vaccine before 20 weeks of pregnancy. Earlier studies also showed that the vaccine is safe later in pregnancy as well—for both pregnant people and their babies. The CDC emphasized the urgency of vaccination among these groups in a health alert issued on September 29, reporting new data showing a rise in COVID-19-related deaths among pregnant people.

Vaccine prospects

Here are some of the vaccines that have made it to phase three and beyond:

Name:   BNT162b2  

Who: One of the world’s largest pharmaceutical companies, based in New York, in collaboration with German biotech company BioNTech.

What:   A nucleic-acid vaccine that requires two doses taken 21 days apart.  

Approval status: On December 2, the U.K. became the first Western country to approve any COVID-19 vaccine when it authorized the Pfizer-BioNTech candidate—making the drug the first mRNA vaccine in history allowed for human use. The FDA granted emergency use authorization   to this vaccine on December 11, 2020, and fully approved it on August 23, 2021. The vaccine has also been granted emergency approval in Canada, the European Union , and other countries.

U.S. regulators have also approved Pfizer’s vaccine for emergency use in children and adolescents ages five to 15. U.K. regulators have also approved this vaccine for use among adolescents ages 12 to 15, while the European Union granted conditional authorization .

As of September 24 U.S. regulators granted emergency use authorization of a third dose of Pfizer’s vaccine—but only for certain subgroups of the national population, including older people and those with underlying conditions that put them at higher risk of disease and for people in occupational or institutional settings that put them at high risk of infection, such as health-care workers and teachers.

Distribution: Globally, Pfizer expects to be able to produce up to 1.3 billion doses by the end of 2021. Questions have been raised over the vaccine’s storage, which requires ultra-cold freezers set at minus 70 degrees Celsius (-94 degrees F). On February 19, however, Pfizer and BioNTech said that their vaccine can remain stable for two weeks at temperatures between minus 25℃ and minus 15℃ (-13℉ to 5℉), a common range in pharmaceutical freezers and refrigerators. The finding would allow for easier distribution of the vaccine in communities where ultra-cold storage requirements present a challenge.  

Efficacy:   On September 20, Pfizer announced that a study of its clinical trials shows its vaccine is safe and highly effective in children ages five to 11. Researchers determined that two low doses administered three weeks apart elicit high levels of neutralizing antibodies among children, with side effects comparable to those seen in people ages 16 to 25. The 10-milligram doses of vaccine are a third of what has been approved among older age groups. The company later released an analysis of its clinical trials showing that the vaccine is 90.7 percent effective in preventing symptomatic disease among kids in this age group.

Pfizer also expects to release data soon on how well its vaccine works among children ages six months to five years, according to CEO Albert Bourla. In a public forum, he said the data could be available as early as the end of October .

On August 25, Pfizer announced new data showing that a third dose of its vaccine generates robust quantity of neutralizing antibodies that is more than three times higher than what was observed one month after the second dose.

A preprint study out of the United Kingdom shows that the Pfizer and AstraZeneca vaccines remain protective against the Delta variant but that their efficacy wanes over time . Among study participants, Pfizer’s vaccine waned more rapidly. Within four to five months after a second dose, the vaccine’s efficacy was on par with the AstraZeneca shot. The study emphasizes, however, the both vaccines still significantly reduce the risk of infection.  

On July 8, a study published in Nature demonstrated that people who have received both doses of the Pfizer or AstraZeneca vaccines remain fully protected against severe disease, hospitalization, and death from the Delta and Beta variants. However, a single dose of either vaccine was not as protective.

The findings corroborate an earlier study published in Nature showing that the Pfizer and Moderna vaccines elicit “robust and prolonged” immune responses. As the New York Times reported at the time , the findings suggested that people who are immunized with these vaccines may not need booster shots as protection may last for years so long as the virus doesn’t mutate to evade it.

On June 10, a study published in the journal Nature showed that two doses of the Pfizer vaccine protects against several virus variants, including the Delta and Eta variants . The news came a few days after the CDC announced that the Pfizer and Moderna vaccines reduce the risk of infection by 91 percent for fully vaccinated people.  

In April, the CDC released a study of the U.S. vaccine rollout showing that the Pfizer-BioNTech and Moderna vaccines are 90 percent effective in preventing symptomatic COVID-19 in real-world conditions. The study analyzed the efficacy of the two mRNA vaccines among nearly 4,000 health-care workers, first responders, and other frontline workers who were the first to receive the jab in the U.S. It also showed the vaccines are 80-percent effective after one dose. The findings confirmed earlier studies from the U.K. and Israel .

On December 10, the New England Journal of Medicine published the results of Pfizer’s phase three study, showing the vaccine was safe and 95-percent effective in protecting against COVID-19 in people 16 and older. Pfizer and BioNTech have also announced that a phase three trial shows that their vaccine is safe and 100 percent efficacious among children between the ages of 12 and 15, and that it elicited robust antibody responses.  

Safety:   On June 23, the U.S. Food and Drug Administration said it plans to add a warning label to the Pfizer and Moderna vaccines about rare cases of heart inflammation in adolescents and young adults. The news comes after the CDC convened an emergency meeting of its advisory committee to discuss “rare but higher-than-expected” cases of myocarditis and pericarditis among young people who have received the vaccines. The committee acknowledged that these cases are likely linked to the vaccines but that the benefits of the shots outweigh the risks.

Severe allergic reactions following immunization with the Pfizer-BioNTech vaccine have been reported in many countries. White House advisor Anthony Fauci told CNBC in December that some adverse reactions are expected when a vaccine is distributed to a wider population. Regulators in the U.S. and U.K. have also released reports offering reassurances that severe reactions are rare.

Clinical trials status: On November 18, Pfizer and BioNTech announced the conclusion of their phase three trials. The trials launched in July , enrolling a diverse population in areas with significant SARS-CoV-2 transmission. Pfizer later expanded the trial   to include 44,000 people across multiple countries.  

On February 18, Pfizer and BioNTech announced the launch of a phase two/three clinical trial to study the vaccine’s safety and efficacy among 4,000 pregnant women over the age of 18. The companies also launched a phase 1/2/3 study in children between the ages of six months and 11 years.

On June 8, Pfizer said that it would expand its clinical trials to a larger group of children under age 12. After a phase one study showed that the vaccine was safe and effective in a group of 144 children, the clinical trials enrolled up to 4,500 children at more than 90 sites in the U.S., Finland, Poland, and Spain. Pfizer tested a dose of 10 micrograms in children ages 5 to 11, and three micrograms for children from six months to five years old.  

On July 8, Pfizer and Biotech announced that they are developing an updated version of the vaccine that specifically targets the Delta variant .

Johnson & Johnson

Name:   JNJ-78436735

Who:   One of the world’s largest multinational corporations, based in New Jersey, specializing in healthcare and pharmaceutical products.

What: A single-dose vector vaccine. ( Here’s how the Johnson & Johnson vaccine works .)

Approval status: Approved for use in the U.S., Bahrain , Canada, and the European Union.

On October 21 the CDC cleared the way for the U.S. to begin rolling out booster shots of Johnson & Johnson’s vaccine for all people ages 18 and older at least two months after a first dose.  

U.S. regulators also authorized mixing and matching vaccines—such as administering booster doses of the either Moderna or Pfizer vaccine to people who originally received the Johnson & Johnson vaccine. A preprint analysis of a National Institutes of Health study shows that a booster dose of the mRNA vaccines elicit a stronger immune response than another dose of the Johnson & Johnson shot.  

Distribution: On March 2, the U.S. announced that Johnson & Johnson has partnered with its competitor Merck to increase the supply of its COVID-19 vaccine. Merck will dedicate two facilities to producing the vaccine, which could double the amount of available doses. Biden said that the additional doses will allow the U.S. to vaccinate all adults by the end of May.  

On June 11, the New York Times reported that the FDA has told Johnson & Johnson to throw out 60 million doses made at its plant in Baltimore. The news came a day after CNN reported that the U.S. hasn’t sent any shipments of the vaccine since the first week of May due to a lack of supply caused by earlier issues at the plant. On June 10, Johnson & Johnson also announced that the FDA has approved an extension of the shelf life of its vaccine from three to four and a half months.  

Efficacy: In September 2021 Johnson & Johnson announced results of its studies of booster doses. When administered two months after the first jab, the booster is 100 percent effective against severe disease and causes antibody levels to rise four to six times higher than after the first shot. The second dose was also shown to be 75 percent effective against all symptomatic disease globally and 94 percent effective in the U.S. The company said that a booster shot administered six months after the first dose produced a 12-fold increase in antibody levels.

The company also said that real-world evidence shows that its single-dose vaccine remains effective against COVID-19. The press release cited a study published to a preprint server , which shows that the vaccine remains 79 percent effective in preventing COVID-19 and 81 percent effective in preventing hospitalizations. An earlier study conducted by Johnson & Johnson shows that its vaccine offers strong protection against Delta that lasts for at least eight months.  

However, on July 20, the New York Times reported on a preliminary study showing that Johnson & Johnson’s vaccine is less effective against the Delta and Lambda variants than it was against the original virus strain. The paper notes that the results were obtained in a lab experiment and may not reflect the vaccine’s real-world efficacy.

On February 24, an FDA analysis confirmed Johnson & Johnson’s earlier report that its vaccine is safe and effective in preventing COVID-19. The report found the vaccine is 72-percent effective in preventing COVID-19 based on U.S. trials, and 85-percent effective in preventing severe disease across all regions. It also shows that the vaccine was 64-percent effective in preventing disease in the company’s South African trials, which is higher than had previously been reported.

On June 9, a study published in the journal Nature showed that Johnson & Johnson’s vaccine is effective in protecting against virus variants, including the Beta and Gamma variants of concern . The study showed that the vaccine elicits neutralizing antibodies and a T-cell response among people who live in areas where the variants are widely circulating, including Brazil and South Africa.  

Safety: On July 13, U.S. regulators added a warning to Johnson & Johnson’s vaccine in response to rare reports linking the shot to Guillain-Barré Syndrome, a disorder in which the body’s immune system attacks the nerves. The FDA said there have been about a hundred preliminary reports of the syndrome among the 12.8 million people who have received the Johnson & Johnson vaccine. It added that the benefits of receiving the vaccine still outweigh the risks.  

CDC officials told the Washington Post that the cases have mostly been reported about two weeks after vaccination among men , many aged 50 or older, and that these cases will be discussed during an upcoming meeting of the CDC’s advisory committee.  

In the spring, the vaccine’s rollout was briefly halted in the U.S. and across Europe as regulators investigated reports of blood clotting among people who have received the shot. The FDA and CDC reviewed 15 cases of blood clots. The cases—which the agencies noted are “extremely rare”—occurred in women between the ages of 18 and 48 within six to 13 days after vaccination. The Europeans Medicines Agency also said that the cases it reviewed occurred in people under 60—mostly women—within three weeks of vaccination.  

On April 23, the U.S. FDA and CDC lifted the pause on Johnson & Johnson’s vaccine and said that immunizations can resume immediately. The agencies said that the risk of blood clots is “very low” and that the benefits of getting the vaccine outweigh the risks. It will add information about the increased risk of blood clots to the vaccine’s label. The decision came days after the European Medicines Agency said that blood clots should be listed as a “very rare” side effect of Johnson & Johnson’s COVID-19 vaccine.  

Clinical trials status: On September 23, 2020, Johnson & Johnson announced the launch of its phase three “ENSEMBLE” trial to evaluate the safety of the vaccine—and how well it works—among up to 60,000 adults from a variety of countries. The trial included “significant representation” from older populations and those with underlying conditions that make them more susceptible to COVID-19.  

On October 12, 2020, Johnson & Johnson announced that it paused phase three trials for an independent safety review due to an unexplained illness in a participant. The company didn’t provide any details, in part to protect the patient’s privacy, but said that illnesses and accidents are expected in large clinical studies. What’s more, study pauses are routine for clinical trials and aren’t typically reported . Later that month, the company announced it would resume trials, which were fully enrolled with 45,000 participants by December 17.

On November 15, 2020, Johnson & Johnson launched a second phase three trial to study the safety and efficacy of a two-dose regimen of its vaccine candidate in up to 30,000 volunteers worldwide. The study intends to assess whether a second dose of the vaccine will offer longer-lasting protection.

On April 2, Johnson & Johnson announced that it has begun vaccinating children age 12 to 17 as part of its phase 2a clinical trial. The company said it will initially test the vaccine in adolescents age 16 to 17 before expanding it to younger children.

Moderna Therapeutics

Name: mRNA-1273  

Who:   A Massachusetts-based biotech company, in collaboration with the National Institutes of Health.

What: A nucleic-acid vaccine that requires two doses.  

Approval status: On December 18, the FDA granted emergency approval to Moderna’s COVID-19 vaccine, making it the second available in the United States. The vaccine has also been approved in the European Union , Canada , the U.K. , Israel , and by the WHO .

On October 21 the CDC cleared the way for some people to get booster shots of the Moderna vaccine. The agency endorsed the FDA’s emergency use authorization of booster doses for all people ages 65 and older, as well as those ages 18 to 64 who are at risk of severe COVID-19 because of their underlying conditions. It also includes people ages 18 to 64 who are at high risk of exposure because of where they work or live, such as health-care workers or incarcerated people.

Moderna has applied for full FDA approval of its COVID-19 vaccine for use in people age 18 and older. The company also plans to file for emergency use authorization for teens ages 12 to 17.  

On October 5, Moderna announced that European Union regulators have authorized a third dose of its COVID-19 vaccine for “severely immunocompromised” people ages 12 and older.  

Distribution: The FDA has said that Moderna’s vaccine can now be kept at room temperature for up to a day. The vaccine can otherwise be safely stored on ice or in a normal refrigerator for 30 days. These changes are expected to help the company distribute its vaccine more quickly.

The company plans to deliver at least 500 million doses globally per year beginning in 2021, thanks in part to a deal it has struck with Swiss manufacturer Lonza that will allow it to manufacture up to a billion doses a year.  

Efficacy: A study of clinical trials among adolescents ages 12 to 17 shows that its vaccine is safe and 100 percent effective. The study also showed the vaccine is 93 percent effective among participants in this age group two weeks after the first dose.

Moderna has said that the phase two clinical trials of its booster dose showed that a third dose administered six months after the second “induce robust antibody responses” and increased protections against the variants of concern. It has also said that a study of the phase two clinical trials of its three booster candidates produced robust antibody responses against the virus, including the Gamma, Beta, and Delta variants of concern.  

However, there is some doubt about whether people who received the Moderna shot will need boosters. A study published in the journal Nature in June 2021 showed that the vaccine elicits “robust and prolonged” immune responses—indicating that protection may last for years so long as the virus doesn’t mutate to evade it.

On September 10, the CDC released a study of more than 32,000 real-world cases suggesting that Moderna’s vaccine is more effective at preventing hospitalizations than the Pfizer or Johnson & Johnson vaccines. The overall efficacy of Moderna’s vaccine was 95 percent, compared to 80 percent for Pfizer and 60 percent for Johnson & Johnson.  

The study backed up earlier studies suggesting that Moderna’s vaccine may provide stronger protection than Pfizer’s jab. A study published on August 30 found that Moderna’s vaccine produces significantly more neutralizing antibodies than Pfizer’s, which might be attributed to the higher dosage or the longer interval between the first and second doses. On August 8, a preliminary Mayo Clinic study of more than 50,000 patients showed that the efficacy of Moderna’s vaccine dropped from 86 percent in early 2021 to 76 percent in July, when the Delta variant was predominant. Meanwhile, the Pfizer vaccine’s efficacy dropped over the same time period from 76 percent to 42 percent.  

An earlier preprint analysis of Moderna’s vaccine also suggested that antibody levels can predict the vaccine’s efficacy against COVID-19. The study showed that people with breakthrough infections who had lower levels of antibodies in their blood were more likely to develop symptomatic infections than those with higher levels of antibodies. The study authors tell Nature that the data doesn’t suggest a threshold of antibodies that ensures protection but it does show a relationship between higher levels of antibodies and lower risk of infection .

On August 12, a study published in the journal Science showed that Moderna’s vaccine protects against COVID-19 for at least six months and is effective against the Delta variant. The findings confirm earlier studies and announcements made by the company that its vaccine remains 93 percent effective for at least six months after administration of the second dose.

On July 9, Nature reported on a study showing that two quarter-doses of Moderna’s vaccine generates long-lasting neutralizing antibodies and T cells . The results suggest that it might be possible to administer fractional doses to help stretch the world’s vaccine supply, particularly in low- and middle-income countries that are facing shortages.

On February 17, the New England Journal of Medicine published a preliminary report showing that Moderna’s vaccine remains effective in protecting against the virus variant found in the U.K. However, it may be less effective in protecting against the South African variant—although researchers noted that further study is needed.  

In December 2020, an FDA analysis of the phase three study of Moderna’s vaccine confirmed that it is 94.1-percent effective in preventing mild cases of COVID-19 and 100-percent effective at preventing severe cases after taking two doses.

Safety:   On June 23, 2021, the U.S. Food and Drug Administration said it planned to add a warning label to the Pfizer and Moderna vaccines about rare cases of heart inflammation in adolescents and young adults. The news comes after the CDC convened an emergency meeting of its advisory committee to discuss “rare but higher-than-expected” cases of myocarditis and pericarditis among young people who have received the vaccines. The committee acknowledged that these cases are likely linked to the vaccines but that the benefits of the shots outweigh the risks.

Clinical trials status: Moderna announced on December 17, 2020, that it was launching clinical trials to evaluate the vaccine’s safety in children and people with cancer ; it will also establish a “pregnancy registry ” to track the vaccine’s safety in people who are pregnant.  

The company started the third phase of its clinical trials in July 2020. Preliminary findings from its phase one trials showed that healthy subjects— including elderly patients —produced coronavirus antibodies and a reaction from T cells, another part of the human immune response. Phase three tested the vaccine in 30,000 U.S. participants.  

On February 24, Moderna announced that it has shipped doses of a booster vaccine to the U.S. National Institutes of Health for clinical trials. The phase one trial will determine whether the booster can improve immunity against the South Africa variant. Moderna is also investigating using a third dose of its approved vaccine to protect against variants.  

AstraZeneca-University of Oxford

Name: ChAdOx1 nCoV-19  

Who: The U.K. university, in collaboration with the biopharmaceutical company AstraZeneca.

What: A viral vector vaccine that requires two doses.

Approval status:   Approved for use in the United Kingdom, the European Union, Argentina, India, and other countries. It has also been authorized by the World Health Organization.

Efficacy: In August 2021 a preprint study out of the United Kingdom showed that the Pfizer and AstraZeneca vaccines remain protective against the Delta variant but that their efficacy wanes over time . Among study participants, Pfizer’s vaccine waned more rapidly. Within four to five months after a second dose, the vaccine’s efficacy was on par with the AstraZeneca shot. The study emphasizes, however, both vaccines still significantly reduce the risk of infection.

On July 8, a study published in Nature demonstrated that people who have received both doses of the AstraZeneca of Pfizer vaccines remain fully protected from the Delta and Beta variants. However, a single dose of either vaccine was not as protective.

On June 25, preliminary results from a British study showed that mixing doses of the AstraZeneca and Pfizer vaccines provides strong protection against COVID-19. Researchers told the New York Times that the protection is strong regardless of the order in which the vaccines are administered. The findings will be useful for those who are unable to get a second AstraZeneca vaccine due to production delays and safety concerns, although researchers say it’s still best to get two doses of the same vaccine for now.

On March 24, AstraZeneca released the primary analysis of its U.S. phase three clinical trials showing that its vaccine is 76 percent effective at preventing COVID-19, slightly lower than the 79 percent efficacy it had announced two days earlier based on a partial analysis of the data. It is also 85 percent effective in people 65 and older and 100 percent effective at preventing severe cases of the disease.

U.S. health officials had taken the unusual step of questioning the decision to release the interim results , describing them as “outdated and potentially misleading.” In a letter obtained by the Washington Post , an independent panel of experts at the National Institutes of Health that oversees U.S. clinical trials said that it had recommended the company release a later analysis instead, showing the vaccine may be 69 to 74 percent effective.

The companies also said that the vaccine’s efficacy increased to 82 percent when the second dose was taken after 12 weeks or longer, rather than the originally recommended four-week interval. The British government has recommended the longer gap in its rollout of the vaccine to prioritize getting the first shot to as many at-risk people as possible.  

On February 7, South Africa halted its use of the AstraZeneca-Oxford vaccine after preliminary laboratory studies showed it offered only minimal protection against the virus variant that is dominant in that country. The finding was later confirmed by a study published in the New England Journal of Medicine showing that the vaccine does not protect against mild to moderate cases of COVID-19 caused by the South African variant. Early data suggested   that the vaccine will still effectively protect against the variant that is prevalent throughout the U.K.    

Safety: On June 9, a study published in the journal Nature Medicine found that people who have received the AstraZeneca vaccine have a slightly increased risk of a bleeding disorder. The analysis of 2.53 million people who received the vaccine found an incidence of 1.13 cases per 100,000 vaccines. Researchers said the benefits of getting the vaccine outweigh the risks. The study echoed an earlier safety review conducted by the European Medicines Agency .

In Canada, meanwhile, on June 29 regulatory officials advised people with a history of capillary leak syndrome against receiving the AstraZeneca vaccine. Health Canada i s also updating the vaccine’s label to add the syndrome as a potential side effect.

Distribution: Project members say their candidate can be stored at temperatures seen in common refrigeration. Oxford and AstraZeneca expect to produce up to three billion doses of the vaccine in 2021.

On December 30, the U.K. announced changes to its vaccine delivery plan to prioritize delivering the first dose of either vaccine to as many at-risk people as possible, based on data provided to and released by health regulators. It did so by delaying administration of the second dose of the AstraZeneca-Oxford drug. A similar rule was issued for the Pfizer-BioNTech vaccine, but regulators didn’t provide   data to back the   new regimen. Overall, the U.K. still recommends that recipients receive two doses of either vaccine for maximum benefit.  

Clinical trials status:   On December 11, AstraZeneca and Russia’s Gamaleya Institute announced plans to work together to study the possibility of combining Oxford’s vaccine with Gamaleya’s Sputnik V vaccine. Since both use the same adenovirus, researchers will investigate whether a combination of the two will improve efficacy.  

The AstraZeneca-Oxford vaccine’s phase three trial aimed to recruit up to 50,000 volunteers in Brazil, the U.K., the United States, and South Africa. On September 8, AstraZeneca paused the trials for a safety review due to an adverse reaction in one participant in the U.K., which the company described as a “routine action.” After an investigation by independent regulators, the trials resumed in the U.K., Brazil, South Africa, and India in September and resumed in the U.S. a month later.

Name:   NVX-CoV2373

Who: A biotechnology company based in Gaithersburg, Maryland.

What: A protein vaccine that involves a nanoparticle carrier to better aid delivery and uptake by cells. The vaccine is administered in two doses, 21 days apart.  

Approval status: Authorized for emergency use in Indonesia.

Novavax has not yet submitted its vaccine to the FDA for emergency use authorization, but it is planning to do so . Reuters reports that Novavax also said that it will file a separate application for booster shots once the emergency use authorization submission is processed; the company said its booster shot given six months after the two-dose regimen elicited a 4.6-fold increase in antibodies. The company has filed for authorization from regulators in India and the Philippines.

Efficacy and safety: On June 14, Novavax announced that its vaccine is safe and 90.4 percent effective in protecting against COVID-19—including the more contagious virus variants that are circulating. The vaccine is also 100 percent effective at preventing moderate and severe disease among 29,960 clinical trial participants age 18 and older in the U.S. and Mexico.  

On March 11, Novavax announced that a final analysis of its phase three clinical trials in the U.K. shows that its vaccine is 96.4-percent effective in preventing COVID-19. It also announced the findings of its phase 2b clinical trial in South Africa, which showed the vaccine was only 48.6-percent effective against the strains circulating there. Both trials showed the vaccine is 100-percent effective at preventing severe cases of the disease.  

On January 28, 2021, Novavax had announced preliminary results of its phase three trials in the U.K., which showed at the time that its vaccine is 89.3-percent effective in preventing COVID-19. On September 2, 2020, a study of the company’s phase one trial published in the New England Journal of Medicine found that the vaccine was safe and produced coronavirus antibodies at a higher level than is seen among those who have recovered from COVID-19. It also stimulated T cells, another arm of the human immune response.

Clinical trials status: On September 24, 2020, Novavax announced the launch of its phase three trial in the United Kingdom, which evaluated the vaccine in up to 10,000 people, both with and without underlying conditions. Up to 400 participants were also vaccinated against the seasonal flu as part of a sub-study to help determine whether it is safe to give patients both vaccines at the same time. On November 30, Novavax said it had completed enrollment in its phase three trial in the U.K.

On December 28, 2020, Novavax announced the launch of a phase three study in the U.S. and Mexico, which evaluated the safety and efficacy of its vaccine in up to 30,000 adults.  

Name: None  

Who: China’s state-run pharmaceutical company, in collaboration with the Wuhan Institute of Biological Products.

What: Two inactivated SARS-CoV-2 vaccines.  

Approval status: China has approved one of the company’s vaccines for general use and another for limited use. One of the Sinopharm vaccines has also been approved by the World Health Organization as well as in Bahrain, the United Arab Emirates, and other countries.

Sinopharm filed for final regulatory approval from China in late November, two months after the New Yorker reported that hundreds of thousands of Chinese civilians have already been vaccinated under the government’s emergency-use approval. China began to innoculate medical workers and other high-risk groups with the Sinopharm trial vaccines in July, making it the first experimental vaccine available to civilians beyond clinical volunteers.  

Efficacy and safety:   On July 19 preliminary results from a study conducted in Sri Lanka found that Sinopharm’s vaccine was less effective against the Delta variant than the original SARS-CoV-2 strain. As Reuters reported, the study showed that the vaccine elicited a 1.38-fold reduction in antibody levels against the variant.

On May 7, the World Health Organization estimated the Sinopharm vaccine’s efficacy to be 79 percent among all age groups, affirming the company’s earlier announcement of the results of its phase three study.

Preliminary findings from two randomized trials, published in the Journal of the American Medical Association , have shown the vaccine can trigger an antibody response with no serious adverse effects. The study did not measure T cell-mediated immune responses. These results are significant, though, as they are the first published data from human clinical trials for a COVID-19 vaccine that uses a whole, inactivated virus.

Clinical trials status: Sinopharm launched its first phase three trial in July 2020 among 15,000 volunteers—aged 18 to 60, with no serious underlying conditions—in the UAE. The company selected the UAE because it has a diverse population made up of approximately 200 nationalities, making it an ideal testing ground. Sinopharm also conducted phase three trials in locations such as Peru and Bahrain .

Name:   CoronaVac  

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Who:   A Chinese biopharmaceutical company, in collaboration with Brazilian research center Butantan.

What: An inactivated vaccine.  

Approval status:   Approved for limited use by the WHO as well as in China, Indonesia, Brazil, and other countries.

Efficacy and safety: On July 15 Reuters reported that the leaders of a Chilean study have recommended administering a third dose of Sinovac’s vaccine as its efficacy has waned in the face of the Delta variant. The vaccine’s level of protection is lower than others—late-stage trials found that it is 51 percent effective in preventing COVID-19. Still, Nature reports that it is 100 percent effective at preventing severe disease and therefore is key to helping curb the pandemic.  

On April 7, a preliminary study of CoronaVac’s vaccine rollout in Brazil showed that the vaccine is about 50 percent effective in protecting against COVID-19 in a region where the highly transmissible P.1 variant is circulating.  

Clinical trials status: CoronaVac entered phase three trials in July, with plans to recruit nearly 9,000 healthcare professionals in Brazil, in addition to phase three trials in Indonesia . A planned trial in Bangladesh was delayed, after Bangladesh refused in October to co-finance a late-stage trial.  

Center for Genetic Engineering and Biotechnology

Name: Abdala

Who: A government-run research institute in Cuba.

What: A protein subunit vaccine that’s administered in three doses.

Approval status: Approved for emergency use in Cuba and Vietnam. Prior to granting emergency use authorization, Cuba had already begun administering the vaccine among health workers as part of an “intervention study.”

Efficacy and safety: On June 22 Cuba announced that the Abdala vaccine is 92.28 percent effective against COVID-19.  

Clinical trials: In March Cuba launched phase three clinical trials for the Abdala vaccine among 48,000 volunteers.

Finlay Institute for Vaccines

Name: Soberana-02

What: A conjugate vaccine that uses part of the virus spike protein.

Approval status: Authorized for emergency use in Cuba and Iran.

Efficacy: On June 22 the New York Times reported that the Soberana-02 vaccine was 62 percent effective at preventing COVID-19 after two of its three required doses.  

Clinical trials:   On March 4, Cuba became the first country in Latin America to announce the launch of a phase three clinical trial for one of its COVID-19 vaccines, the Miami Herald reported. The Cuban government said the phase three trial would be conducted in Havana among 44,000 volunteers.

Name: CVnCoV

Who:   A German biopharmaceutical company in partnership with Bayer , a German multinational pharmaceutical company.

What: An mRNA vaccine that’s administered in two doses taken 28 days apart.

Approval status: Not approved for use. On October 12, 2021, CureVac announced that it was withdrawing its COVID-19 vaccine candidate months after it reported disappointing results from a study of its clinical trials showing its vaccine was only 47 percent effective in preventing COVID-19, falling short of the company’s own criteria for success. CureVac attributed its results to the virus variants that were circulating at the time. It sequenced 124 cases of COVID-19 among clinical trial participants and found only one case was caused by the original SARS-CoV-2 virus and more than half were caused by variants of concern.

Efficacy and safety:   On January 11, CureVac announced that preliminary results show its vaccine prompted robust antibody and T-cell responses in rhesus macaques.  

Clinical trials status: On December 14, 2020, CureVac announced it had begun enrolling participants in a phase 2b/3 study to assess its vaccine’s safety and efficacy in more than 35,000 participants in Europe and Latin America. One week later, the company launched a separate phase three trial in healthcare workers in Mainz, Germany.

Sanofi and GSK

Who:   A global biopharmaceutical company in partnership with a global healthcare company.

What: An adjuvant-supported recombinant-protein vaccine.

Approval status: Not approved for use.

Efficacy and safety: On May 17, the companies announced that a study of their phase two clinical trials shows the vaccine generated a high level of neutralizing antibodies with no safety concerns.

Clinical trials: On May 27, 2021, Sanofi and GSK announced that they had started to enroll participants in a phase three clinical study to test the safety and efficacy of their vaccine in 35,000 volunteers ages 18 and older in the U.S., Asia, Africa, and Latin America. The study’s broad geographic range was intended to allow the companies to evaluate the vaccine’s efficacy against variants of concern.

Biological E. Limited

Who: An Indian vaccine and pharmaceutical company in partnership with the Baylor College of Medicine.

What: A protein-based subunit vaccine that requires two doses administered 28 days apart.

Latest news: On April 26, the companies announced that they received approval to launch a phase three clinical trial of their vaccine candidate. The trial will evaluate the efficacy and safety of the vaccine among more than 1,200 volunteers ages 18 to 80 at 15 sites across India.

Distribution: If the vaccine is approved for use, it will be distributed through the COVAX Facility, a global effort to ensure the equitable distribution of COVID-19 vaccines.

Name: VLA2001

Who: A vaccine developer based in France.

What: An inactivated virus, adjuvant-supported vaccine, with two doses administered three weeks apart.

Approval status: Not approved for use. The company has initiatied rolling submission for approval with U.K. and European regulators.

Safety and efficacy:   On October 18 Valneva announced that its vaccine elicited higher antibody levels than the AstraZeneca vaccine and “significantly fewer” adverse events among participants age 30 and older.

On April 6, Valneva announced that a study of its phase 1 and 2 clinical trials show that its vaccine prompted a strong immune response with no safety concerns.

Clinical trials: On April 21 Valneva announced the launch of phase three clinical trials to study the safety and efficacy of its COVID-19 vaccine compared to that of AstraZeneca’s conditionally approved vaccine. Approximately 4,000 volunteers were expected to receive two doses of either vaccine to determine the immune response of each. Valneva says it hopes to file for regulatory approval in the fall of 2021.

Shenzhen Kangtai Biological Products

Name: None.

Who: A China-based pharmaceuticals company

What: An inactivated vaccine that requires two doses administered 28 days apart.

Approval status: Authorized for emergency use in China. The country approved the Kangtai shot for emergency use in May 2021, just weeks after the vaccine launched its phase three clinical trials.

Clinical trials:   Kangtai’s phase three clinical trials are underway , testing the vaccine’s safety and efficacy among 28,000 adults age 18 and older.

Name: CoVLP

Who:   A Canadian biotechnology company, in partnership with British multinational pharmaceutical company GlaxoSmithKline.

What: A plant-derived recombinant vaccine with an adjuvant that requires two doses administered 21 days apart.

Efficacy and safety:   In May 2021 Medicago reported that interim data from its phase two clinical trial showed that its COVID-19 vaccine elicited high levels of neutralizing antibodies with no severe adverse reactions.

Clinical trials: On March 16, Medicago and GlaxoSmithKline announced that their vaccine had entered phase three clinical trials to study its safety and efficacy in up to 30,000 volunteers in 10 countries, including Canada and the U.S.

Bharat Biotech

Name:   COVAXIN

Who: An Indian biotechnology company, in collaboration with the Indian Council of Medical Research and the National Institute of Virology.

What:   An inactivated vaccine, which requires two doses that are administered 28 days apart.  

Approval status:   Authorized for emergency use in India , Mexico, the Philippines, and other countries. The WHO has also listed the vaccine for emergency use.

Efficacy and safety: In November 2021 the WHO   said that its analysis of COVAXIN shows the vaccine is 78 percent effective against COVID-19 and “is extremely suitable for low-and-middle-income countries due to easy storage requirements.”  

On March 3 Bharat Biotech announced that an interim analysis of its phase three trial showed its vaccine is 81-percent effective in protecting against COVID-19 after the second dose. A separate preliminary study also indicated that the vaccine produces antibodies that can neutralize the virus variant that originated in the U.K.  

On January 21, The Lancet published interim findings from COVAXIN’s phase one study that showed the vaccine elicited an immune response in participants. The study identified only one serious adverse event, and it was unrelated to the vaccine.

Clinical trials status: On November 16, Bharat Biotech announced it had begun phase three trials involving 26,000 participants at more than 25 centers across India.

The Gamaleya National Center of Epidemiology and Microbiology

Name: Sputnik V

Who: A Russian research institution, in partnership with the state-run Russian Direct Investment Fund.

What: A viral vector vaccine that uses two strains of adenovirus and requires a second injection after 21 days to boost the immune response.  

Approval status:   In August, Russia cleared the Sputnik V vaccine for widespread use and claimed it as the first registered COVID-19 vaccine on the market—before the vaccine’s phase three trials had begun and despite the lack of published evidence at the time. It has since been approved in Belarus, Argentina, Venezuela, and other countries.  

On March 4 the European Union announced that it would begin a rolling review of the Sputnik V vaccine. The announcement came after a handful of European countries said they would consider approving the vaccine without E.U. approval. Hungary has already authorized the vaccine. But on October 21 Reuters reported that European regulators are unlikely to make a final decision until early 2022.

Efficacy and safety: On February 2, the medical journal The Lancet published the results of a phase three trial in Moscow that found the Sputnik V vaccine is safe and 91.6-percent effective in preventing COVID-19. The study, which involved more than 22,000 participants, also showed the vaccine is 100-percent effective in preventing moderate or severe cases of the disease, as no such cases were confirmed at least 21 days after receiving the first dose.  

Distribution: Global demand for Sputnik V soared in the weeks after the vaccine’s efficacy data was published. The vaccine makers reached deals with more than 40 countries in Latin America, Eastern Europe, Asia, and Africa. On February 19, the African Union announced that Russia has offered them 300 million doses of the Sputnik V vaccine.  

Clinical trials status: On December 11, the Gamaleya Institute and biopharmaceutical company AstraZeneca announced they will work together to study the possibility of combining Sputnik V with the candidate that AstraZeneca has developed with the University of Oxford. Since both candidates use the same adenovirus, researchers will investigate whether combining them will improve efficacy of the AstraZeneca vaccine, which is 70.4-percent effective in preventing COVID-19.  

Chumakov Center

Name:   CoviVac

Who: A Russian research center.

What: An inactivated vaccine given in two doses, 14 days apart.

Approval status: On February 20, Russia approved the CoviVac vaccine for use even though late-stage clinical trials to test its safety and efficacy have not yet begun. Reuters reports that early-stage trials with 200 participants showed the vaccine has no side effects.

Distribution: The Chumakov Center plans to produce half a million doses per month.

Murdoch Children’s Research Institute

Name: Bacillus Calmette-Guerin BRACE trial  

Who: The largest child health research institute in Australia, in collaboration with the University of Melbourne.

What: For nearly a hundred years, the Bacillus Calmette-Guerin (BCG) vaccine has been used to prevent tuberculosis by exposing patients to a small dose of live bacteria . Evidence has emerged over the years that this vaccine may boost the immune system and help the body fight off other diseases as well.  

Efficacy and safety:   On November 10, 2020, a U.S. study published in the Journal of Clinical Investigation found that among 6,201 healthcare workers in Los Angeles, those who had previously received the BCG vaccine reported symptoms of COVID-19 less often than those who hadn’t, a finding that study authors say strengthens the case for further research. In October of that year, the U.K. launched a study of the BCG vaccine that is part of the Australian-led trials. The study is seeking to recruit a thousand frontline health-care workers to test the vaccine’s effectiveness against COVID-19.  

Clinical trials status: In Apri 2020, researchers from the Murdoch Children’s Research Institute began a series of randomized controlled trials that will test whether BCG might work on the coronavirus as well. They aim to recruit 10,000 healthcare workers in the study. In an April 2020 scientific brief, the World Health Organization found that there is no current evidence that the BCG vaccine protects people against infection with the coronavirus.  

CanSino Biologics

Name: Ad5-nCoV

Who: A Chinese biopharmaceutical company.

What: A viral vector vaccine.  

Approval status: On June 25, 2020, CanSino became the first company to receive limited approval to use its vaccine in people even though it was still in the second phase of its clinical trials. At the time, the Chinese government pproved the vaccine for military use only, for a period of one year. Since then, the vaccine has been approved in China, Argentina, Hungary, and other countries.

Efficacy and safety: Preliminary results from phase two trials, published in The Lancet , have shown that the vaccine produces “significant immune responses in the majority of recipients after a single immunisation.” There were no serious adverse reactions documented.

Clinical trials status: On December 21, CanSino announced that it has recruited more than 20,000 participants for its phase three trials in Pakistan, Russia, Mexico, and Chile. On August 15, Russian biopharmaceutical company Petrovax announced it had launched the first phase three clinical trial of Ad5-nCoV.

Vector Institute

Name: EpiVacCorona

Who: A Russian biotechnology institute.

What: A protein vaccine, namely it uses small fragments of viral antigens called peptides to produce an immune response.

Approval status: On October 14, 2020, Russia granted regulatory approval to EpiVacCorona even though the vaccine candidate had not published any results and had not entered phase three of its clinical trials. It is the second vaccine candidate that Russia approved for use despite a lack of published evidence about its safety and efficacy. It has since been approved for use in Turkmenistan and authorized for emergency use in Belarus.

Efficacy and safety: On January 13, 2021, Russian state news agency TASS reported that of the more than 2,000 volunteers who had received both doses of EpiVacCorona’s two-dose regimen, none reported adverse reactions from the vaccine.  

Clinical trials: In November 2020 Russia launched mass trials of its EpiVacCorona vaccine; the trials will inoculate 150 people over the age of 60 and 3,000 volunteers over the age of 18.

Zydus Cadila

Name: ZyCoV-D

Who: An Indian pharmaceutical company.

What: A DNA-based vaccine that is delivered by a skin patch .

Approval status: Approved for emergency use in India.

Safety and efficacy: In December 2020 Zydus Cadila said that a combined phase one/two study of its vaccine showed it was safe and prompted an immunogenic response, but the company did not share any data.

Clinical trials: On January 3, 2021, Zydus Cadila announced it had received approval from Indian regulators to launch a phase three trial testing the safety and efficacy of its vaccine in about 30,000 volunteers.

Anhui Zhifei

Name: ZF2001

Who: A Chinese biopharmaceutical company, in partnership with the Institute of Microbiology at the Chinese Academy of Sciences.

What:   A subunit vaccine that uses pieces of protein from a pathogen to trigger an immune response.

Approval status: Approved for use in China, Indonesia, and Uzbekistan.

Efficacy and safety: In August 2021 a study of the company’s phase one and two clinical trials published in The Lancet   showed that the vaccine elicited neutralizing antibodies and that the most common adverse reactions were cough, fever, and headache.

Clinical trials: In November 2020 Chinese health officials announced the launch of phase three trials for the Anhui Zhifei vaccine. The trials—which aimed to recruit 29,000 volunteers aged 18 or older—were expected to be conducted in China, Indonesia, Pakistan, and Ecuador.

Research Institute for Biological Safety Problems

Name: QazCovid-in

Who: A research institute in Kazakhstan.

What: An inactivated vaccine.

Approval status: Granted temporary registration in Kazakhstan in January 2021 despite a lack of data from its phase three clinical trials.

Efficacy and safety:   In August 2021 a study of the vaccines phase one and phase two clinical trials published in The Lancet found that the vaccine was safe with no severe adverse events recorded. The studies also found the vaccine elicited a neutralizing antibody response as well as a T-cell response.

Clinical trials status: In December 2020, the institute announced that the Kazakh Ministry of Health approved the launch of phase three trials to assess the vaccine’s safety and efficacy in 3,000 volunteers.

Institute of Medical Biology at the Chinese Academy of Medical Sciences

Name: Unknown

Who: A Chinese research institute.

What: An inactivated vaccine that requires two doses taken 14 days apart.

Clinical trials: In December 2020, researchers launched phase three clinical trials to test the efficacy and safety of the vaccine in 34,020 participants in Malaysia and Brazil.  

Safety and efficacy: Preliminary results of the vaccine’s phase one trial showed that it prompted an immune response with no serious adverse incidents.

Editor's note: This story was originally published on July 31, 2020. It was regularly updated as developments occurred until November 2021.

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A two-dose schedule could make HIV vaccines more effective

Mit researchers find that the first dose primes the immune system, helping it to generate a strong response to the second dose, a week later..

One major reason why it has been difficult to develop an effective HIV vaccine is that the virus mutates very rapidly, allowing it to evade the antibody response generated by vaccines.

Several years ago, MIT researchers showed that administering a series of escalating doses of an HIV vaccine over a two-week period could help overcome a part of that challenge by generating larger quantities of neutralizing antibodies. However, a multidose vaccine regimen administered over a short time is not practical for mass vaccination campaigns.

In a new study, the researchers have now found that they can achieve a similar immune response with just two doses, given one week apart. The first dose, which is much smaller, prepares the immune system to respond more powerfully to the second, larger dose.

This study, which was performed by bringing together computational modeling and experiments in mice, used an HIV envelope protein as the vaccine. A single-dose version of this vaccine is now in  clinical trials , and the researchers hope to establish another study group that will receive the vaccine on a two-dose schedule.

“By bringing together the physical and life sciences, we shed light on some basic immunological questions that helped develop this two-dose schedule to mimic the multiple-dose regimen,” says Arup Chakraborty , the John M. Deutch Institute Professor at MIT and a member of MIT’s Institute for Medical Engineering and Science and the Ragon Institute of MIT, MGH and Harvard University.

This approach may also generalize to vaccines for other diseases, Chakraborty notes.

Chakraborty and Darrell Irvine, a former MIT professor of biological engineering and materials science and engineering and member of the Koch Institute for Integrative Cancer Research, who is now a professor of immunology and microbiology at the Scripps Research Institute, are the senior authors of the study, which  appears today in  Science Immunology . The lead authors of the paper are Sachin Bhagchandani PhD ’23 and Leerang Yang PhD ’24.

Neutralizing antibodies

Each year, HIV infects more than 1 million people around the world, and some of those people do not have access to antiviral drugs. An effective vaccine could prevent many of those infections. One promising vaccine now in clinical trials consists of an HIV protein called an envelope trimer, along with a nanoparticle called SMNP. The nanoparticle, developed by Irvine’s lab, acts as an adjuvant that helps recruit a stronger B cell response to the vaccine.

In clinical trials, this vaccine and other experimental vaccines have been given as just one dose. However, there is growing evidence that a series of doses is more effective at generating broadly neutralizing antibodies. The seven-dose regimen, the researchers believe, works well because it mimics what happens when the body is exposed to a virus: The immune system builds up a strong response as more viral proteins, or antigens, accumulate in the body.

In the new study, the MIT team investigated how this response develops and explored whether they could achieve the same effect using a smaller number of vaccine doses.

“Giving seven doses just isn’t feasible for mass vaccination,” Bhagchandani says. “We wanted to identify some of the critical elements necessary for the success of this escalating dose, and to explore whether that knowledge could allow us to reduce the number of doses.”

The researchers began by comparing the effects of one, two, three, four, five, six, or seven doses, all given over a 12-day period. They initially found that while three or more doses generated strong antibody responses, two doses did not. However, by tweaking the dose intervals and ratios, the researchers discovered that giving 20 percent of the vaccine in the first dose and 80 percent in a second dose, seven days later, achieved just as good a response as the seven-dose schedule.

“It was clear that understanding the mechanisms behind this phenomenon would be crucial for future clinical translation,” Yang says. “Even if the ideal dosing ratio and timing may differ for humans, the underlying mechanistic principles will likely remain the same.”

Using a computational model, the researchers explored what was happening in each of these dosing scenarios. This work showed that when all of the vaccine is given as one dose, most of the antigen gets chopped into fragments before it reaches the lymph nodes. Lymph nodes are where B cells become activated to target a particular antigen, within structures known as germinal centers.

When only a tiny amount of the intact antigen reaches these germinal centers, B cells can’t come up with a strong response against that antigen.

However, a very small number of B cells do arise that produce antibodies targeting the intact antigen. So, giving a small amount in the first dose does not “waste” much antigen but allows some B cells and antibodies to develop. If a second, larger dose is given a week later, those antibodies bind to the antigen before it can be broken down and escort it into the lymph node. This allows more B cells to be exposed to that antigen and eventually leads to a large population of B cells that can target it.

“The early doses generate some small amounts of antibody, and that’s enough to then bind to the vaccine of the later doses, protect it, and target it to the lymph node. That’s how we realized that we don’t need to give seven doses,” Bhagchandani says. “A small initial dose will generate this antibody and then when you give the larger dose, it can again be protected because that antibody will bind to it and traffic it to the lymph node.”

T-cell boost

Those antigens may stay in the germinal centers for weeks or even longer, allowing more B cells to come in and be exposed to them, making it more likely that diverse types of antibodies will develop.

The researchers also found that the two-dose schedule induces a stronger T-cell response. The first dose activates dendritic cells, which promote inflammation and T-cell activation. Then, when the second dose arrives, even more dendritic cells are stimulated, further boosting the T-cell response.

Overall, the two-dose regimen resulted in a fivefold improvement in the T-cell response and a 60-fold improvement in the antibody response, compared to a single vaccine dose.

“Reducing the ‘escalating dose’ strategy down to two shots makes it much more practical for clinical implementation. Further, a number of technologies are in development that could mimic the two-dose exposure in a single shot, which could become ideal for mass vaccination campaigns,” Irvine says.

The researchers are now studying this vaccine strategy in a nonhuman primate model. They are also working on specialized materials that can deliver the second dose over an extended period of time, which could further enhance the immune response.

The research was funded by the Koch Institute Support (core) Grant from the National Cancer Institute, the National Institutes of Health, and the Ragon Institute of MIT, MGH, and Harvard.

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University of Western Australia

In the rare event of a vaccine injury, Australians should be compensated

This article by Professor Nicholas Wood from The Children's Hospital at Westmead Clinical School, University of Sydney, Senior Lecturer Sophie Wenn from the Faculty of Medicine, The University of Queensland and Tim Ford, Senior Lecturer in Paediatrics at the School of Medicine, The University of Western Australia originally appeared in The Conversation on 24 September 2024.

Vaccination is one of the most effective methods to protect individuals and the broader public from disease. Vaccines are typically given to healthy people to prevent disease, so the bar for safety is set high.

People benefit from vaccination at an individual level because they’re protected from disease. But for some vaccines, strong community uptake leads to “herd immunity”. This means people who are unable to be vaccinated can be protected by the “herd”.

As with any prescribed medicine, vaccines can cause side effects. In the rare case that COVID vaccines did cause a specified serious injury (the scheme listed certain conditions that a person could claim for), Australians have been able to claim compensation. But this ends at the end of this month.

From then, Australians won’t be able to access no-fault compensation for any vaccine injury – from COVID or any others.

Why compensate people for vaccine injuries?

Fortunately, serious vaccine injuries are rare. Most are not a result of error in vaccine design, manufacturing or delivery, but are a product of a small but inherent risk.

As a result, people who suffer serious vaccine injuries cannot get compensation through legal mechanisms. This is because they can’t demonstrate the injury was caused through negligence.

Vaccine injury compensation schemes compensate people who have a serious vaccine injury following administration of properly manufactured vaccines.

The COVID vaccine claims scheme

In 2021, in recognition of the rare risk of a serious vaccine injury, and in support of the roll out of the COVID vaccine program, the Australian government introduced a COVID vaccine claims scheme.

The aim was to provide a simple, streamlined process to compensate people who suffered a moderate to severe vaccine injury, without the need for complex legal proceedings. It was limited to TGA-approved COVID vaccines, and to specific reactions.

The Australian government has said the scheme will close this month and claims need to be lodged before September 30 2024.

Following its closure, Australia will not have a vaccine injury compensation scheme.

Australia is lagging internationally

Australia lags behind 25 other countries including the United States, United Kingdom and New Zealand which have comprehensive no-fault vaccine injury compensation schemes. These cover both COVID and non-COVID vaccines.

The schemes are based on the ethical principle of “reciprocal justice”. This acknowledges that people acting to benefit not just themselves but also the community (for the benefit of the “herd”) should be compensated by the same community if it has resulted in harm.

So what happens in Australia now?

In Australia, people with non-COVID vaccine injuries or COVID vaccine injuries not covered by the current claims scheme must bear the costs associated with their injury by themselves or access publicly funded health care. They will not receive any compensation for their injury and suffering.

Australia’s National Disability Insurance Scheme (NDIS) provides funding support to access therapies for people with a permanent and significant disability. However, it does not cover temporary vaccine-related injuries.

Participants with vaccine injuries as a result of taking part in a clinical vaccine trial are compensated. This typically includes income-replacement, personal assistance expenses and reimbursement of expenses resulting from the incident, including medical expenses.

In Australia, we also have strong compulsion for people to receive routine vaccines through legislative requirements such as No Jab No Pay (which requires children to be immunised to receive some government payments) and, in some states, No Jab No Play (which requires children be fully immunised to attend childcare).

Countries such as ours that mandate vaccination without providing no-fault injury compensation schemes for rare vaccine injury could be abrogating the social contract by not protecting the individual and community.

It’s time to set up an Australian scheme

The Australian immunisation system is among the most comprehensive in the world. Our government-funded national immunisation program provides free vaccines for infants, children and adults for at least 15 diseases.

We also have a whole-of-life immunisation register and comprehensive vaccine safety surveillance system.

A recent Senate committee recommended: " the Australian government consider the design and compensation arrangements of a no-fault compensation scheme for Commonwealth-funded vaccines in response to a future pandemic event."

Vaccines are designed to be very safe and effective. But the “insurance policy” of an injury compensation scheme, if designed and communicated appropriately, should build trust and give confidence to health workers and the general public to support our national vaccine program. This is particularly important given the reductions in uptake of routine vaccines.

How should it work?

A no-fault vaccine injury compensation scheme could be funded via a vaccine levy system, as is done in the US, where an excise tax is imposed on each dose of vaccine.

An effective vaccine injury compensation scheme needs to be:  accessible, with low legal and financial barriers;  transparent, with clear decision-making processes, compensation frameworks and funding responsibilities;  timely, with short, clear timeframes for decision-making; fair, with people compensated adequately for the harm they’ve suffered.

Legislation to introduce and allocate funds to support an Australian injury compensation scheme for all vaccines is overdue. The draft National Immunisation Strategy 2025–2030 hinted at the opportunity to explore the feasibility of a no fault compensation scheme for all vaccines the Australian government funds, without committing to such a program.

An Australian vaccine injury scheme, covering all national immunisation program vaccines, not just pandemic use vaccines, should be seen as a crucial component of our public health system and a social responsibility commitment to all Australians.

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• NEWS FEATURE
• 01 June 2021

New vaccine approaches present new possibilities, but new challenges

• Mark Zipkin 0

Mark Zipkin is a freelance writer covering the pharmaceutical and biotech industries.

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You have full access to this article via your institution.

The pace of development for vaccines against SARS-CoV-2 was extraordinary. RNA vaccine company Moderna was shipping vials for clinical testing at the US National Institute of Allergy and Infectious Disease (NIAID) just 6 weeks after accessing a draft of the virus’s genome, built upon decades of research and platforms years in the making. In one regard, the timing of the pandemic was fortuitous, in that novel vaccine technologies that could be rapidly applied to respond to the threat had already been evaluated in clinical trials. But it also laid bare the work left to do to prepare for the future.

The foundation for the latest wave of vaccine technologies rests on government and industry investments in basic research and novel technology platforms, says Gary Nabel, President and CEO of multispecific immunotherapy company ModeX Therapeutics. Nabel cofounded ModeX in 2020 after leaving Sanofi, where he had been CSO since 2012, following more than a decade as head of the Vaccine Research Center at NIAID. According to Nabel, improved understanding of both viruses and human immunology over the past few decades has allowed for the rational design of vaccines in a way that was never possible before. For example, “There really has been an explosion in our understanding about both the determinants of viral spikes that can be recognized by neutralizing antibodies, and the mechanisms by which viruses can enter cells,” he said. “Those two things together gave a lot of insight.”

Other factors were important as well, Nabel says. For one, in the USA, the experience of previous viral outbreaks prepared government agencies such as the Food and Drug Administration (FDA), which carved a clear regulatory path for vaccines via Emergency Use Authorizations (EUAs), and the Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA), which handled vaccine procurement under Operation Warp Speed.

Pandemic proving ground

All three COVID-19 vaccines that have been issued EUAs by the FDA are built on platforms so new that they still haven’t produced a fully approved vaccine in the USA (Fig. 1).

The first two COVID-19 vaccines granted an EUA are based on the mRNA platforms pioneered by Moderna and German immunotherapy company BioNTech, which partnered with Pfizer for clinical development, manufacturing, commercialization and distribution of vaccines for COVID-19 in March 2020. mRNA encodes a protein—in the case of COVID-19 vaccines it is the SARS-CoV-2 spike protein, which the virus needs to bind and invade human cells. The mRNA vaccines prompt human cells to produce the protein, recognize it as a foreign antigen and make antibodies, mimicking the natural immune response to a viral infection.

Moderna spent years exciting investors with its mRNA platform and endeavoring to live up to it. In 2018, it closed a $604 million IPO, the biggest ever for a biotechnology company. On the eve of the pandemic, Moderna had 11 vaccines or therapies in early-stage clinical trials, while BioNTech had 6 cancer vaccines in the clinic. Still, it took nearly $1 billion from Operation Warp Speed to push Moderna’s COVID-19 vaccine through phase 2 and phase 3 clinical trials. Operation Warp Speed also signed a manufacturing agreement worth up to $1.525 billion in August 2020. BioNTech and Pfizer signed a $2 billion manufacturing contract for their COVID-19 vaccine through Operation Warp Speed in July 2020, but did not receive R&D funding.

The adenovirus platform at Johnson & Johnson’s Janssen unit that produced the third SARS-CoV-2 vaccine to receive an EUA, JNJ-78436735, was slightly more mature, having scored its first European Commission approval last July with the Ebola vaccine Zabdeno. Adenovirus vaccines have been tested in the clinic for years, but had struggled to take hold until recently. In the 1990s, adenoviruses were explored as delivery vehicles for gene therapies in diseases such as cystic fibrosis, but their tendency to provoke an immune response was more desirable in a vaccine. The vaccines are based on recombinant adenoviruses, modified to block their ability to replicate or cause illness, that deliver genes for producing an antigen—again, in the case of JNJ-78436735 and others using viral vectors that have received regulatory approval in countries outside the USA, that means the SARS-CoV-2 spike protein.

One benefit to an adenovirus vector such as type 26 (Ad26) used in J&J’s vaccine is that “it’s a relatively easy virus to work with, to insert antigens in, and to make lots of vaccines with,” said Jay Nelson, director of Oregon Health & Science University (OHSU)’s Vaccine and Gene Therapy Institute. Another is that the body recognizes it as a pathogen and mounts an immune response.

Fig. 1 | Comparison of selected vaccines in development against COVID-19. a | Nucleic acid vaccines. b | Adenovirus-based vaccines. c | Recombinant protein vaccine plus adjuvant.

Testing the limits

There is a flipside to the body’s pointed immune reaction to viral vectors that could limit their effectiveness though. “When you use a viral vector, you have to worry about two things: how prevalent that virus is in population, and if you give repeat administration, whether that could give an adverse response,” said Nabel. According to Nabel, the immune system responds to both the adenovirus and the inserted gene, meaning anyone previously exposed to the natural variant of that adenovirus strain would generate antibodies to the vaccine. This pre-existing immunity to the vector effectively reduces the dose, and Nabel thinks it’s one reason why Janssen might have wanted JNJ-78436735 to be a single dose: boosters may be less effective. “In many cases that can be a limitation,” said Nabel, “because the immune system seems to do better, in general, when it sees the same thing more than once. That’s how you generate memory responses.”

For its part, Janssen—which has also tested Ad26 vaccines to prevent Zika, HIV, and respiratory syncytial virus (RSV)—has found no consistent pattern in clinical trials between baseline Ad26-neutralizing antibodies and immune response to its vaccines.

Other companies have attempted to lessen the issue by developing platforms based on adenoviruses that do not naturally infect humans. AstraZeneca’s COVID-19 vaccine, Vaxzevria (AZD1222)—granted emergency authorization in the UK and conditional approval in Europe earlier this year—was developed at the University of Oxford based on a chimpanzee adenovirus, ChAdOx1. “A lot of people in developing countries have already been infected with adenovirus, but they wouldn’t have been exposed to the chimpanzee one,” said Nelson. AstraZeneca has not yet applied for an EUA in the USA.

Still, said Nelson, exposure to the vector in one vaccine might prevent an effective immune response to any future vaccines made from that vector.

And not all adenovirus vectors are the same. For example, adenovirus type 5 (Ad5) has been utilized by China’s CanSinoBIO for its Convidecea vaccine, as well as in the booster following an Ad26-based prime dose in Russia’s Sputnik V vaccine. But the approach has concerned some experts, including researchers who previously tested Ad5-based vaccines for HIV, who have linked it to increases in HIV infection.

mRNA vaccines are delivered in lipid nanoparticles, meaning they don’t trigger the same immune response over multiple doses. As additional, resistant viral SARS-CoV-2 strains have emerged, mRNA companies have quickly developed boosters against the variants. But the lipids can still trigger some inflammation and immune response. “I suspect that’s at least part of the reason why people get these side effects when they get an mRNA vaccine,” said Nabel, though he adds that can likely be improved in the future.

Today most mRNA vaccines have stabilization issues that require ultracold storage throughout the supply chain. That requires sophisticated logistical solutions, said Philippe Denoel, Head of External R&D for GlaxoSmithKline (GSK) vaccines. “We have all seen in one year how important this technology platform is, it allows very fast development of vaccine candidates. But it’s not going to be the one and only solution for the future.”

The next wave

All of the current platforms have their limitations, which has kept academics and companies looking to improve on or build on existing technology. One area of broad possibility is adjuvants, which only recently began to advance beyond traditional adjuvants resembling those used in vaccines since the 1930s. Adjuvants improve the potency of vaccines by boosting immune responses, making them extremely important for vulnerable populations, including the elderly, that have reduced immune function, said Nelson. At least one COVID-19 vaccine candidate nearing potential regulatory authorization, Novavax’s NVX-CoV2373, combines a full-length SARS-CoV-2 spike protein in a recombinant nanoparticle with a saponin adjuvant, and it has been highly efficacious in phase 3 testing.

Another example is Shingrix, a vaccine developed from GSK’s AS01 adjuvant platform and approved by the FDA in 2017 to prevent shingles in adults aged 50 years and older. AS01 is a liposome-based adjuvant with two immunostimulants that GSK has also used to develop a malaria vaccine, Mosquirix, which is approved in Europe. “We’ve seen with Shingrix that using an adjuvant has made all the difference between having an OK vaccine versus one that’s really quite effective,” said Nabel.

Denoel says investments in the AS01 platform also led to the development of additional adjuvants such as AS03, which has been used to improve on GSK’s influenza and COVID-19 vaccine candidates. “The adjuvant platform has been a major investment for us in research and development over 25 years,” he added.

Others are using the limitations of existing platforms to inspire new approaches. Nelson took cues from adenovirus research as his team developed VIR-1111, an HIV vaccine delivered instead by a replication-impaired, persisting cytomegalovirus. No adenovirus-based vaccine for HIV has made it to phase 3 testing, and Nelson suggested that they are better suited for acute infections like COVID-19. The cytomegalovirus approach “might be a way to get around persistent infections, like simplex or other herpesviruses.” Vir Biotechnology licensed the platform through a merger with the OHSU spinout, TomegaVax and now has VIR-1111 in phase 1 trials.

Nabel also noted that nanoparticle technologies are promising approaches. “In the lab, we can mount specific parts of virus to synthetic nanoparticles, which will spontaneously assemble and present them in an array to the immune system,” triggering a more active immune response, he added. Other companies, including Capricor Therapeutics and Codiak BioSciences, are developing exosomes—naturally derived nanoparticles—as potential vaccine delivery systems.

GSK has several other vaccine technologies in development, says Denoel. One is through a partnership with LimmaTech Biologics, to develop next-generation recombinant glycoconjugate vaccines. The company is also tapping a structural biology platform, exploring how vaccine antigens like the RSV prefusogenic fusion protein structure and the coronavirus spike protein can inform future vaccine development.

Investing in the future

Infectious disease research is a team sport, by any measure. “It’s a different business model from other therapeutics,” said Nabel. The number of patients tends to vary, year on year, and vaccine trials require large sets of patients.

Funding for research and development is often bolstered by public bodies and public–private partnerships. Partnership is foundational to GSK’s approach, says Denoel, and support from the Bill & Melinda Gates Foundation and other funders was crucial for development of Mosquirix. He also noted that the Wellcome Trust, and public funders like BARDA and the NIH have been necessary for GSK’s work on Ebola, and the Innovative Medicines Initiative—a public–private partnership developed by the European Commission—brings an important support to the development of new pertussis and RSV vaccines.

The European Commission is also launching its response to BARDA, the European Health Emergency Preparedness and Response Authority (HERA), this year. Denoel called this a welcome addition to the world of biopreparedness.

Public funding in particular has been notable in the past year as governments signed huge procurement deals that provided the financial incentives to get COVID-19 vaccines across the finish line, such as the $456 million vaccine order signed in March 2020 by Johnson & Johnson—before its clinical trials had even begun—with BARDA. But Vered Caplan, CEO of personalized cell and gene therapy company Orgenesis, notes that many vaccine technologies, including mRNA, might not exist without basic research funding from NIH. “We should look at where these technologies are coming from,” she said. “This is taxpayer money being invested into academic institutes. This information belongs to everyone, in a way we don’t always realize.”

NIH priorities guided the creation of Nelson’s institute two decades ago, down to the interdisciplinary staff he recruited. “I hired in people that would have their own programs,” he said, “but the idea was, we would all work together on programs, because we knew that the NIH was going to be funding people in this direction. And that’s been quite successful.” The institute has two contracts with NIH to develop new adjuvants—one of the institute’s priorities, he said—including one working with immunotherapy company Inimmune. “The NIH has been extremely helpful in forming these types of partnerships, which I think are really necessary to get new vaccines out there,” he said.

Still, there are some things that can’t be done in an academic lab. It was the Gates Foundation, working with OHSU on its HIV vaccine, that pushed several OHSU researchers to co-found Vir, said Nelson, which raised $143 million in an IPO in 2019 and now has a market cap of $6.3 billion. “We couldn’t take it any further, we needed somebody that had expertise in vaccine manufacturing and clinical trials,” Nelson added.

Pre-pandemic, private investment had been more supportive of viral vaccine-adjacent companies, like BioNTech and Moderna, which focused more in areas like immunotherapy. “I wish that it could be the reverse, that thanks to investments in infectious disease, or biopreparedness vaccine technologies, this could instead open up opportunities for the treatment of other important situations like oncology, antibiotic resistance or non-communicable diseases” said Denoel. He remains optimistic, however. “I think the situation has somewhat changed, they realize that infectious disease offers not only opportunities to bring solutions to important medical needs and public health, but also could translate into some kind of financial returns for them.”

Viral vaccines remain risky business, though. “We’ve had a little bit of an infusion of talent and resources,” said Nabel. “I don’t know how long that will last. The same thing happened with Ebola—as soon as it was no longer a threat, everybody said, ‘Forget that, who wants to work on Ebola vaccines?” Only time will tell whether COVID-19 has the same fate.

doi: https://doi.org/10.1038/d43747-021-00079-x

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