YouTwo votes each, 13-1, were cast by the U.S. Centers for Disease Control and Prevention’s immunization committee. They recommended that Americans get an Omicron specific booster dose of COVID-19 vaccine. The panel recommended boosters from two manufacturers—Pfizer-BioNTech and Moderna, both of whom make mRNA-based vaccines; the new booster made by Pfizer-BioNTech is for people 12 years and older, and the Moderna shot is for adults 18 years and older. It was also suggested that patients wait at least two months from the end of their last booster shot before receiving one of two additional ones. CDC director Dr. Rochelle Walensky now takes the committee’s decision into consideration and will decide whether to accept the recommendation.
The CDC’s guidance comes a day after the U.S. Food and Drug Administration (FDA) authorized the Omicron-specific shots by both companies.
This booster was the first vaccine to attack a SARS-CoV-2 variant. All vaccines approved by FDA, recommended by CDC, and booster doses authorized by agencies, have targeted the original virus which emerged in 2019. Omicron boosters now target the BA.4/BA.5 subvariants, which account for almost all COVID-19 new infections in America.
Omicron BA.4/5 booster marks a major shift in the approach health officials want to take in protecting the public. Rather than recommending booster doses every few months, as they’ve been advising since the vaccines became available in late 2020, they are now hoping to shift to an immunization schedule that mimics that for influenza, with an annual shot. Omicron boosters will be replaced by the newly approved Omicron booster. No matter how many booster doses they’ve received, anyone 12 or older can get one.
In recommending the booster shot, the CDC’s panel of independent vaccine experts acknowledged that while they have authorized boosters before, this one is different in a number of ways. Not only is it the first to target a variant of the virus, it’s also the first to contain genetic material against two versions of the virus—the original, or ancestral strain, and Omicron BA.4 and BA.5, in a so-called bivalent vaccine. In the case of both Pfizer-BioNTech’s and Moderna’s booster, the dose is the same as the previous boosters that have been authorized, but split between the original and Omicron BA.4/5 strains.
The most worrying aspect for committee members is that boosters made by both companies haven’t been proven effective in protecting people against COVID-19. After a June FDA panel meeting, Moderna and Pfizer BioNTech developed Omicron boosters. Moderna requested vaccine makers target the BA.4/BA.5 subvariants. They had created a booster that combined Omicron’s original strain with an older version, BA.1, which showed it could boost Omicron-fighting antibodies. Ba.4/BA.5 rapidly outnumbered BA.1 when it came to causing infection, so the FDA demanded a bivalent vaccine containing BA.4/BA.5. In August, both companies provided data from animal studies that showed their boosters increased antibody levels in mice to FDA.
FDA and CDC scientists insist that animal data are sufficient to recommend the newest booster given all evidence that supports the safety and efficacy of vaccines. These scientists point to real-world data that includes millions of people who had been vaccinated twice with the original vaccine as well as data regarding the bivalent BA.1 boost, which has never seen the light of day. Dr. Doran Fink, deputy clinical director of the division of vaccines and related products applications at FDA, opened the discussion by telling the members that, “FDA in its authorization considered the totality of evidence, which consisted primarily of an extrapolation approach based on data from clinical trials with similar bivalent vaccine formulations consisting of the original and Omicron BA.1 sub lineage component, as well as extensive experience with the use of the original monovalent vaccine both as a primary series and as boosters. Additionally, FDA considered supportive data from some animal studies that provided additional reassurance about our extrapolation approach.”
That’s a different approach than that taken by U.K. and Canadian health authorities, who decided to authorize the bivalent booster made by Moderna against the BA.1 subvariant.
This leaves Omicron BA.4/BA.5 booster recommendation to some U.S. public health specialists in doubt. Dr. Pablo Sanchez, professor of pediatrics at Ohio State University and the lone dissenter in voting against recommending the new Omicron booster, said: “I feel we really need human data. It’s a new vaccine, a new platform, and there is a lot of vaccine hesitancy already, so we need human data. I really feel this is premature and wish we had seen that human data.”
Sanchez, however, acknowledged that he would still probably get the booster, since he was convinced by the FDA’s argument that the available evidence, even if it’s indirect, suggests the new shot is both safe and potentially effective. There’s also the fact that every year, the annual flu shot is approved without data demonstrating effectiveness against the latest influenza strains circulating, making the immunization a bit of a gamble, albeit a calculated one. “I would remind the committee that every year, we recommend influenza vaccines based on new strains without clinical studies being done,” said Dr. Melinda Wharton, from the CDC’s National Center for Immunization and Respiratory Diseases and executive secretary of the CDC commmittee. “In a lot of ways, this is analogous to that.”
CDC researchers supported recommending a modification to the booster. They discovered that those who had been immunized with Omicron BA./BA.5 have experienced waning protection and sometimes very little immunity. The original boosters and vaccines prevent people getting seriously sick. However, this protection seems to be waning as people with more complete immunizations become moderately ill when they are infected. CDC scientists showed that if human trials on BA.4/5 booster were not finished by November, 137,000 additional people could be hospitalized, and close to 10,000 people would become COVID-19-infected.
That’s the reason behind the government’s push to authorize the new booster, but it’s not clear if the public will follow health officials’ advice and rush to get boosted—especially in an environment in which people are weary of repeated boosters and increasingly skeptical of their effectiveness. People who are infected by the Omicron BA.4/5 strain will believe that they have immunity and can get boosters if necessary. And some health officials aren’t convinced that BA.4/5 booster provides that much additional protection from disease compared to the original vaccine, which becomes even more questionable when it comes to people who have been immunized and boosted, and who have recently been infected with Omicron BA.4/5, as many Americans have recently. Dr. Paul Offit, a professor at Children’s Hospital of Philadelphia and a member of the FDA’s vaccine expert committee, does not feel there is enough data to support recommending the new booster, and likely won’t line up for this shot. “The authorization and recommendation by the CDC doesn’t change the data, which is uncomfortably scant,” he tells TIME. “We still have no human data on this vaccine. I don’t plan to get this vaccine, mostly because I don’t think I need it. I have had three previous doses and one mild natural infection.”
The CDC committee was presented with data that addressed the question of what incremental benefits most people who have been vaccinated or boosted will receive from an Omicron-specific booster. While it makes biological sense to match the booster shot to the circulating virus, which is currently the Omicron BA.4/5 subvariant, the studies haven’t been completed yet. The early data in animals are encouraging, suggesting that boosting with the Omicron-specific shot may help people build broader immunity to not just the original strain but also to multiple variants, including Alpha, Beta, Delta, and Omicron, but mouse data can’t substitute for human trials.
They are currently conducting studies on humans and hope to release the results in a couple of months. In the meantime people will have the ability to make decisions about whether or not they want to receive the latest booster dose. “I think this is a big step forward toward simplification,” Wharton told the committee. “I hope we are moving toward something that is simpler and will not require such frequent changes going forward. Clearly we are not there yet, but I think this is a big step forward.”
US government already bought 170 million Omicron B.4/5 booster doses from these two manufacturers. Pfizer BioNTech already has sent 100,000 doses to the 62 destinations that received them on Sept. 1. Following the Labor Day weekend the company will deliver more than 3,000,000 doses to more then 3,000 sites. Moderna is manufacturing 66 million doses to meet the government’s order, but has not reported how many have been shipped so far.
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