OA panel of experts, convened by U.S. Food and Drug Administration (FDA), voted 19-2 to amend the vaccines used from December 2020 in order to prevent COVID-19.
Changes to the vaccine will not apply to people already vaccinated. However, the Omicron subvariant has not been determined by the committee. Omicron produced many variants starting with BA.1 to BA.4 and BA.5, respectively. The latter two are responsible for nearly all cases of COVID-19 in the U.S. The idea of including an Omicron strain into the next booster is very similar to how flu viruses are replaced every year in order to provide the best immunity possible against any version.
The committee’s decision is based on several lines of evidence, including the fact that Omicron is different from the original version of the virus in the currently approved vaccines. Both the original COVID-19 vaccines and the approved booster doses in the U.S. all target an older strain of the virus, known as D614G by public health professionals as the “ancestral strain”.
Experts also heard data from the U.S. Centers for Disease Control and Prevention, which showed that the original vaccines were no longer effective in protecting against Omicron variant and subvariants. Although the vaccines provide excellent protection from becoming seriously ill and dying from COVID-19, experts in public health have provided convincing evidence to suggest that the protection may be stronger if a new vaccine is used.
Is a vaccine needed now for this condition?
The FDA committee decided that it’s time to update the COVID-19 vaccine and that continuing to boost with the existing shot will not provide the durable protection that people need. Experts reviewed the data regarding the dominant Omicron variant. It has been in circulation in the U.S.A since December 20,21 and has already produced several subvariants including BA.1, BA.2.12.12, BA.4, and BA.5.
The same FDA committee had met in April to discuss the criteria for changing the COVID-19 vaccine and concluded that it would take into consideration the advice of the World Health Organization’s Technical Advisory Group on COVID-19 Vaccine Composition (TAG-Co-VAC), which analyzes data on COVID-19 vaccine effectiveness and makes recommendations about when to change vaccines if that effectiveness shows signs of waning, just as a similar WHO group does for the flu vaccine each year. That group concluded in June that while the currently available vaccines made by Moderna and Pfizer-BioNTech continue to protect against severe COVID-19 disease—even if people are infected with Omicron variants—stronger immunity against Omicron could come with a booster dose with a new Omicron-containing vaccine. Dr. Kanta Subbarao, director of the WHO Collaborating Center for Reference and Research on Influenza, explained to the committee the reasoning behind the group’s advice, noting that adding an Omicron-specific component to the next booster would increase the breadth of protection people might receive from immunization. “It’s not so much matching what [virus strain]is most likely to circulate but less about how to achieve broader immunity [against the existing variants],” she told the committee.
Subbarao showed data showing that Omicron infected patients who were immunized and then infected by SARS had a greater range of antibodies. These antibodies were stronger than the ones generated by people unvaccinated who infected only with Omicron.
The WHO did not, however, recommend switching to an Omicron-specific vaccine to immunize people who have not been vaccinated yet, since there isn’t data yet to support whether that immunity would be robust enough.
Additionally, the FDA committee considered other evidence. They found that Omicron-contaminated SARS CoV-2 variants that are currently in circulation are distinct enough from the virus the vaccines aim to protect against, as well as that existing vaccines have less effectiveness in Omicron protection than in other types. Although the existing vaccines still protect against severe diseases, there is a decline in the number of viruses-fighting antibodies within vaccinated persons, especially those who have had booster shots.
After reviewing all data available, FDA Panel decided there was sufficient evidence to warrant changing COVID-19’s booster to more effectively target Omicron variants responsible for most infections.
What version of Omicron is the next target vaccine?
The most polarizing question caused by this question was among both the panel members and invited speakers. Subbarao of WHO proposed that BA.1 be included in the next vaccine. This was due to its genetic differences from current SARS-CoV-2 vaccines. Dr. Peter Marks (FDA) disagreed and preferred to concentrate on BA.4 or BA.5. “The current vaccines appear to be the least effective against them,” he said.
Moderna and Pfizer BioNTech shared data about new vaccines that they have developed. These vaccines contain the original strain of SARSCoV-2 and the one which targets Omicron variant BA.1 in what are called bivalent vaccines. The flu shot typically targets three influenza strains. This is similar to this approach.
Companies also created and tested vaccines for the BA.1 Omicron variety, but they found that mixing the Omicron with original strains resulted in a wider immunity against other Omicron strains.
The task of the committee wasn’t to decide which Omicron version should be used in the booster shot. However, members of the panel favored Omicron versions BA.4 and BA.5 as these are more prevalent in the U.S. However, there are not enough data to determine if BA.4 or BA.5-containing vaccines work well. The committee members encouraged companies to study those versions as Moderna and Pfizer BioNTech do.
The new vaccine will offer better protection against Omicron.
That’s the hope, although there is still limited data from the real world on how much stronger the protection against Omicron will actually be. Companies tested the ability of their bivalent vaccines to create virus-fighting antibodies in a laboratory against Omicron. The committee then extrapolated the results from these studies to determine if the amount of antibodies was sufficient to protect against disease and infection.
It’s not clear whether people vaccinated with the bivalent vaccine targeting BA.1 will produce the same levels of antibodies against the newer Omicron subvariants, including BA.4 and BA.5, as against BA.1. Moderna has begun to study the effects of its BA.1 bivalent vaccination on immune responses to BA.4/BA.5. Pfizer BioNTech also provided data from an early mouse study. These data revealed that the bivalent vaccine produced antibodies against BA.4 strains and BA.5 strains but at lower levels than those against BA.1 strains. Both companies are still studying their potential vaccines to combat Omicron subvariants. These will most likely increase in frequency over the next few months.
Is the vaccine safe?
Some members of the Committee questioned whether bivalent vaccines that target different SARS CoV-2 strains might cause more side effect, such as myocarditis. Myocarditis is an inflammation and swelling of the heart that mostly affects adolescents. Moderna and Pfizer BioNTech provided short-term data that was reviewed by FDA. They found side effects and adverse reactions in the vaccines within a month of vaccination. However, longer-term follow-up will be needed.
Are there any other vaccines that could be developed in the coming year?
The committee also saw data from Novavax, which makes a COVID-19 vaccine using a different technology from the mRNA platform behind Moderna and Pfizer-BioNTech’s vaccines. The FDA is still reviewing the company’s request for emergency use authorization and has not yet made a decision. But many committee members were impressed with the data from the Novavax’s original vaccine candidate, which targets the original SARS-CoV-2 strain but generated strong immune responses to a variety of variants, including against Omicron. Dr. Glenn Gregory, the company’s president of research and development, argued that the data made a good case for deploying Novavax’s vaccine, with at two doses, to better fight the current Omicron cases. But because that vaccine isn’t authorized, and the data haven’t been reviewed by the FDA yet, it’s not clear how valid that evidence is.
Is it possible to get the latest booster doses?
Moderna, Pfizer BioNTech and Moderna have both begun to manufacture bivalent vaccines targeted at BA.1. Moderna indicated that the U.S. could make hundreds of million of these doses in July and August if it decides to boost.
However, if regulators approve a bivalent vaccine containing BA.4 and BA.5 strains of vaccine, the companies will need to produce those shots for three months and submit FDA reviews. Those vaccines won’t be made available until November or October unless approved by FDA or CDC.
Now that the FDA’s advisory committee recommends including some version of Omicron in the next booster shot, it’s up to the FDA to review the available data, or ask for additional data from the vaccine makers, to decide which Omicron strains to include and when people should be boosted. The panel’s decision is only the first in a long series of steps—and more studies—that are required before anyone receives a new COVID-19 vaccine in the fall. “What I’d like to see are additional data, and better understanding of the clinical meaningfulness on the impact on severe outcomes and disease,” said Adam Berger, director of clinical and healthcare research policy at the National Institutes of Health. “I’d like further data on the long-term durability of any type of change to the actual vaccine composition.”
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