WWith almost all new COVID-19 infections in the US coming from the Omicron BA.4 and BA.5 subvariants, it makes sense that health officials are considering switching to a different vaccine to protect the public.
White House COVID-19 Response Coordinator Dr. Ashish Jha wait the first Omicron-specific booster will be available in mid-September at the earliest, if the injection is cleared and recommended by the US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). In late August, both Pfizer-BioNTech and Moderna submitted applications to the FDA for authorization of their Omicron-specific boosters.
But with fall and winter fast approaching, the seasons when respiratory viruses like SARS-CoV-2 spread even more efficiently, as students head back to school and people crowd indoors. , preparing the reinforcement requires a more efficient regulatory and review process. And that includes considering safety and efficacy data from animals, not people.
In June, the FDA’s panel of independent vaccine experts met to consider switching the country to a new booster targeting Omicron, given how quickly that variant is dominating new infections. At the time, the two largest COVID-19 vaccine makers, Pfizer-BioNTech and Moderna, which make mRNA-based vaccines, had developed injections against an earlier Omicron variant, BA.1. The panel decided that if the health authorities were to change the booster injection to target Omicron, the next one should protect against the BA.4 and BA.5 subvariants, which would continue to account for almost all cases in the winter season.
They asked the vaccine manufacturers to develop a new vaccine, one that combined the original vaccine and also targeted Omicron BA.4 and BA.5. In late August, both companies submitted data on their new bivalent vaccines to the FDA for emergency use authorization.
However, given the short time they had to develop the injection, the data only included information on the safety and efficacy of the booster in animals. Human studies are planned and will continue even if the FDA and CDC decide to license the injections and the government begins distributing them. The FDA has also decided to review the animal study data without further consultation with its advisory committee.
That has vaccine experts divided. dr Paul Offit, a member of the advisory committee, says this strategy makes him “uncomfortable” for several reasons. He notes that the data presented by Pfizer-BioNTech and Moderna in June on their BA.1 booster vaccine, which focused on the levels of antibodies that fight the virus that the vaccine generated, was disappointing. “They showed that neutralizing antibody titers were between 1.5 and two times higher against Omicron than the levels induced by an ancestral vaccine booster,” he says. “I would like to see clear evidence of a dramatic increase in neutralizing antibodies, more dramatic than what we saw against BA.1, before launching a new product. We are owed at least that much.
While studies in humans take more time, Offit says that even a small trial involving about 100 people to measure their antibody levels after receiving a BA.4/5 booster would be helpful. “You can stimulate people and measure their neutralizing antibodies two weeks later,” she says. Such information could also be critical in setting realistic expectations for the Omicron booster. The public may feel like it’s a panacea signaling the end of the pandemic, but without any data showing how well the booster will protect people from not only getting sick, there could be unrealistic expectations about what the booster can do. “I get a little nervous, frankly, when I hear this [booster] it’s going to be miraculous,” says Offit.
Other experts see it a little differently. Based on the fact that mRNA vaccines have been given to millions of people so far, with relatively few safety concerns, and given that the vaccines have been effective in protecting people from being hospitalized or dying from COVID-19, even during the latest Omicron surge, they argue that changing the virus strain in the vaccine doesn’t require the same extensive testing that the original shot required. “The totality of the evidence is relevant here,” says Dr. Ofer Levy, director of Boston Children’s Hospital’s precision vaccines program and also a member of the FDA’s vaccine advisory committee. “We are in a situation where we need to pivot as variants emerge, and if we try to be too rigid in our approach, we will always be behind and not provide the population with optimal protection.”
Levy says that the latest Omicron-specific boosters that the FDA is considering contain a combination of mRNA targets against the original virus and Omicron BA.4/BA.5, so the data on safety and efficacy of the original vaccine in the protection against hospitalization and death is relevant. While the data on this vaccine comes from animals, using that data to decide whether or not to authorize the booster is a matter of “hedge bets.” There is data showing that even boosted vaccinated people can get mild to moderate COVID-19 disease because their vaccine-induced protection is waning, so boosting with an injection that is better suited to Omicron sub-variants than circulating now is a reasonable bet, even if the data on their efficacy comes from animals and not people. “I think it’s the right decision,” says Levy.
There is no guarantee that the FDA will authorize the new bivalent vaccines, although all indications point to an authorization that could come in a week or so. When the shots are released and people get the booster, health officials will carefully monitor the data of those vaccinated to ensure that the assumptions they made about the safety and effectiveness of the booster hold up. And hospitalization rates in the coming winter will reveal whether banking on Omicron’s new specific booster was the right move.
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