A Food and Drug Administration advisory panel on Friday unanimously supported giving a third shot of Pfizer and BioNTech's coronavirus vaccine to older adults or to those at high risk of severe COVID-19, but rejected a plan to roll out booster shots more broadly.
The panel was initially asked by the agency whether an additional dose of the companies' vaccine should be approved for anyone 16 or over. But the advisers overwhelmingly opposed, with all but two voting against the proposed recommendation.
Following the 16-2 vote against, the FDA's top vaccine reviewers drafted a new proposal for booster shots in adults over 65 or who are at higher risk of worse outcomes from infection — groups the advisers judged most likely to benefit from an additional dose based on evidence gathered to date. The additional dose would be given at least six months after the initial two-dose vaccination.
"I think we need to target the boosters right now, but specifically to the people who are likely to be at high risk, and it's an older population, it's immunocompromised," Michael Kurilla, one of the committee members, said. The FDA in mid-August authorized booster doses of both Pfizer's and Moderna's vaccines for immunocompromised individuals.
Notably, the committee's recommendation was for an emergency authorization of a third Pfizer shot, rather than an approval as the drugmaker had requested. Members of the panel also supported a third shot for healthcare workers or others whose jobs put them at higher risk of exposure.
While the FDA is not required to follow its advisers' recommendations, it usually does. A decision from the agency is expected in the coming days.
The committee did not weigh in on additional doses for people who received either Moderna's or Johnson & Johnson's vaccine, but their recommendation Friday could influence how the FDA handles other authorizations.
The FDA called Friday's meeting after Pfizer in late August formally requested authorization of a booster dose of its vaccine in people aged 16 years and older. The drugmaker's case drew heavily from immune response data it had collected from a handful of people given a third dose in an early clinical trial, and from some 300 participants in the Phase 3 study that led to the vaccine's initial authorization, and later, approval.
Those results showed an additional dose, given months after the first two, significantly raised levels of neutralizing antibodies against the coronavirus, and appeared similarly safe. Side effects were similar to those that occurred after the second dose, according to the company's presentation.
Pfizer also pointed to data from studies of real-world use compiled by researchers in Israel and by Kaiser Permanente, which show signs of waning protection against infection. The FDA didn't formally vet those data, although agency representatives and advisers discussed them on Friday.
Advisers heard from Israeli health officials, who argued that had the country not begun providing its citizens with a third dose at the end of July, hospitalizations would have risen higher during the fourth wave Israel's now experiencing. Dr. Sharon Elroy-Preiss, director of public health services at Israel's Ministry of Health, said the country had started to see a "trend of severe, critically-ill patients" ranging from ages 40 to 60 who had only received two doses.
"We didn't want to wait to see those results and we knew that we needed to vaccinate a larger portion of the population in order to get the numbers down quickly," she said.
But advisers were concerned about recommending booster shots more broadly while the data on the safety of a third dose in younger adults remains relatively sparse. Top of mind for many was the risk of myocarditis or pericarditis — inflammation in and around the heart.
"If it's related to immune response, and the booster shots induce a very strong response, is that going to amplify the risk of myocarditis?" said James Hildreth, president and CEO at Meharry Medical College in Nashville and a committee member.
While Israeli researchers emphasized they had not yet seen evidence the risk after a third dose is any higher than after a second, advisers pointed out the relatively short follow-up reported so far.
The CDC is currently compiling safety data on the roughly 1 million Americans who've received a third dose to date, an agency official said, and plans to have that analysis ready shortly.
The back-and-forth debate comes roughly one month after the Biden administration publicly announced plans to offer booster shots to most Americans beginning Sept. 20, pending regulators' OK. But the White House's timeline jumped ahead of the scientific decision-making process at the FDA and the Centers for Disease Control and Prevention.
While the heads of both the FDA and the CDC had signed off on the plan, staff and advisers to the agencies seemed more reluctant to green light booster shots widely without more supportive data. The White House's announcement, which administration officials said was meant to help lay the groundwork for boosters ahead of time, reportedly factored into the surprise plans by two of the FDA's top vaccine reviewers to retire this fall.
One of those FDA officials, Marion Gruber, played a prominent role in Friday's meeting, pushing the committee to vote on broader booster use even as it appeared committee members were leaning against the proposal. Gruber, along with the other departing FDA reviewer, recently authored an editorial with World Health Organization leaders arguing against administering booster shots to the general public.
However, despite some signs of tension throughout the meeting, the FDA and its advisers were able to agree on a revised voting question, paving the way for the group's recommendation in older and at-high-risk adults.
Jay Portnoy, a professor at the University of Missouri-Kansas City School of Medicine and committee member, said he'd act immediately on their resolution. "I plan to go out and get my third vaccine," he said.
Advisers to the CDC are scheduled to meet next week and could further refine a recommendation for which groups should receive a booster, particularly who is considered to be at high risk.