Scientific advisers to the US Food and Drug Administration (FDA) have voted not to recommend a third shot of the Pfizer vaccine for Americans older than 16, a potentially significant blow to the Biden administration after it announced a plan to “boost” adults before advisory committees had a chance to review scientific evidence in public.
The committee chair, Dr Arnold Monto, a University of Michigan epidemiologist, said he planned to continue deliberations after the vote. Sixteen of 18 advisers opposed the proposal, even as some members believed there is “a role” for a third dose.
The decision by the vaccines and related biological products advisory committee is not binding, but the FDA usually follows its advice.
The decision came after significant public scientific dissent regarding a third dose of the vaccine. Much of the data in favor of a third dose came from Israel, while data was sparse on whether a booster could help protect people against hospitalization and death.
“There are too many questions for me to feel comfortable saying ‘yes’ to this,” said A Oveta Fuller, a member and associate professor of microbiology and immunology at the Medical School University of Michigan, summing up the views of several voting members.
Another committee member, Dr Eric Rubin, Harvard assistant professor of microbiology and molecular genetics, said he “strongly” suspects the vaccine will be low-risk, “but we don’t have that right now, and I don’t think I’d be comfortable giving it to a 16-year-old for all the reasons everyone has raised”.
The decision throws into question the Biden administration’s plan to “boost” or provide a third Pfizer shot to fully vaccinated Americans older than 16, an effort the administration had said would start 20 September.
Scientists said they had “trouble” supporting the Pfizer application for booster doses because of reasons including the risk of myocarditis, or heart inflammation, in young men especially; a lack of evidence that boosters would significantly curb the direction of the pandemic; and questions about whether boosters should be confined to older Americans.
Much of the debate focused on how vaccines provoked immunity: did waning immunity in mild and moderate disease, which requires circulating antibodies, indicate there would be waning immunity from severe disease requiring hospitalization, which relies on a different part of the immune system?
Several members felt there was insufficient evidence to answer the question.
However, not all voting members agreed.
“Immunity clearly seems to decrease over time,” said Dr Jay Portnoy of Children’s Mercy hospital in Kansas City, a committee member who said he was already prescribing a third dose of the Pfizer vaccine.
“Do we want to wait until more previously vaccinated people get sick before we prevent them from getting sick,” Portnoy said. “I’d rather not get the Covid disease.”