FDA advisers vote not to recommend Pfizer booster shots for most Americans

Scientific advisers to the US Food and Drug Administration (FDA) have voted not to recommend a third shot of the Pfizer vaccine for most Americans, 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.

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The committee chair, Dr Arnold Monto, a University of Michigan epidemiologist, continued deliberations after the vote. Sixteen of 18 advisers opposed the broad proposal for boosters for those older than 16, even as some members believed there is “a role” for a third dose.

After the initial “no” vote, the committee recommended a much smaller number of Americans receive third shots of the Pfizer vaccine at least six months after their first doses, this time under emergency use authorization rather than full approval.

The 18-member panel unanimously recommended a “booster” dose to people older than 65 and at high risk of severe Covid-19. As a result of the emergency use authorization, study will probably continue on booster shots as Pfizer works to achieve full approval.

The advisory panel then further clarified the emergency use authorization should include health workers and those at high risk of “occupational” exposure to Covid-19.

The decision by the FDA’s 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. Much of the data in favor 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, a 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”.

In its application for approval, Pfizer submitted safety data on only about 300 adults aged 18 to 55 who received a booster shot, a sample size several members said was too small.

The decision throws into question the Biden administration’s plan to provide a third Pfizer shot to fully vaccinated Americans older than 16. It also throws into question broader booster plans, which the administration had made sound nearly inevitable.

Another Covid-19 vaccine maker, Moderna, has applied to provide booster shots. Administration officials have not recommended booster shots for people who received the Johnson & Johnson vaccine, though they still may.

All vaccines currently available in the US are highly effective against hospitalization and death from Covid-19. FDA committee members’ questions about “waning” vaccine immunity tended to focus on how effective vaccines remained against preventing infection, transmission and prevention of mild to moderate disease, and whether that would significantly change the direction of the pandemic.

Scientists said they had “trouble” supporting the Pfizer application for booster doses for most Americans for 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.”

There was agreement on the question of waning immunity in older people, who also face the highest risks of severe Covid-19.

The administration’s booster plan for the general public has been criticized by scientists and global health leaders. Dissent intensified as the FDA’s meeting neared, culminating with two scientists leaving the organization over the booster plan.

In an article published in the Lancet, the departed scientists warned: “Current evidence does not appear to show a need for boosting in the general population, in which efficacy against severe disease remains high.”

The benefits of boosting, they said, “will not outweigh the benefits of providing initial protection to the unvaccinated”.

The most potent criticism has argued that providing booster shots to people in wealthy, western nations is not nearly as effective as vaccinating new people around the world, and that providing booster shots necessarily reduces vaccine supply in poorer countries. The FDA excluded this debate from its deliberations.

Regardless of the FDA, some healthy Americans have felt compelled to seek third shots. The US plan for booster shots may have influenced other wealthy nations to roll out booster programs, further reducing available vaccine supply.

There is little debate that third shots are appropriate for people who are immunocompromised and mount a less robust response to the vaccine. The FDA recommended third shots for this group in August.