Publisher Health

WASHINGTON — Two of the Food and Drug Administration’s top vaccine regulators will leave the agency this fall, a development that could disrupt its work on deciding whether to recommend coronavirus vaccines for children under 12 and booster shots for the general population.

Dr. Marion Gruber, the director of the F.D.A.’s vaccines office, will retire at the end of October, and her deputy, Dr. Philip Krause, will leave in November, according to an email that Dr. Peter Marks, the agency’s top vaccine regulator, sent to staff members on Tuesday morning. One reason is that Dr. Gruber and Dr. Krause were upset about the Biden administration’s recent announcement that adults should get a coronavirus booster vaccination eight months after they received their second shot, according to people familiar with their thinking.

Neither believed there was enough data to justify offering booster shots yet, the people said, and both viewed the announcement, amplified by President Biden, as pressure on the F.D.A. to quickly authorize them.

Dr. Marks said he would serve as the acting director of the vaccines office while the agency searched for its next leader. Stephanie Caccomo, a spokeswoman for the agency, said it was “confident in the expertise and ability of our staff to continue our critical public health work.”

Some public health experts have said the administration’s booster shot announcement, which did include a caveat that the F.D.A. would first have to authorize such shots, undermined the agency’s responsibility to make that assessment on its own schedule, led by career scientists. Since Mr. Biden took office in January, the White House has made a point of saying it would not influence the F.D.A.’s work.

Some outside experts have also challenged the booster plan as premature, saying the available data shows that the Pfizer-BioNTech and Moderna vaccines are holding up well against severe disease and hospitalization, including against the Delta variant. Extra shots would be warranted only if the vaccines failed to meet that standard, some have said.

White House officials have stressed that the plan for Americans to start receiving boosters next month was uniformly endorsed by the most senior federal health officials, including Dr. Janet Woodcock, the acting F.D.A. commissioner. They have described the need to develop a booster plan as urgent in light of growing evidence that the vaccines lose potency over time — a trend that they fear suggests the vaccines’ protection against severe disease and hospitalization will also soon weaken.

Officials have singled out data from Israel as a particularly worrisome sign, especially for older adults and other vulnerable groups. Data from abroad “actually has led us to be even more concerned about increased risk of vaccine effectiveness waning against hospitalization, severe disease and death,” Dr. Rochelle P. Walensky, the director of the Centers for Disease Control and Prevention, said at a White House briefing on the pandemic Tuesday.

Asked about reports that Dr. Gruber and Dr. Krause were unhappy with what they viewed as pressure on the agency, Jeffrey D. Zients, the White House’s Covid-19 response coordinator, reiterated that the booster strategy had always been contingent on F.D.A. review.

“As our medical experts laid out, having reviewed all the available data, it is in their clinical judgment that it is time to prepare Americans for a booster shot,” he said at the briefing. “We announced our approach in order to stay ahead of the virus, give states and pharmacies time to plan, and to be transparent with the American people.”

But some critics have said that explanation falls short, because F.D.A. regulators are in the position of trying to determine whether booster shots are safe and effective after the White House — and their own agency head, Dr. Woodcock — already endorsed administering them.

“This process has been the reverse of what we would normally expect in vaccine policy,” with the administration announcing plans based on a certain outcome before regulators can complete their review, said Jason L. Schwartz, an associate professor of health policy at the Yale School of Public Health. “That has made it even more complicated and confusing for the public.”

The announcement of the departures comes at a critical time for the F.D.A. The agency is in the midst of a marathon push to decide several important questions about the three coronavirus vaccines it authorized on an emergency basis over the past year. It is facing public pressure from some quarters to speed up, and from others to slow down. Mr. Biden still has not nominated someone to permanently lead the agency, a post that requires Senate confirmation.

Only about three weeks remain before the Biden administration wants to begin offering boosters to recipients of the Pfizer-BioNTech and Moderna vaccines, starting with nursing home residents, health care workers and others who were inoculated early in the vaccination campaign.

The F.D.A. is currently trying to schedule a meeting of its panel of independent experts, the Vaccines and Related Biological Products Advisory Committee, to discuss booster shots, according to people familiar with the agency’s planning. That meeting would be public, and could potentially reveal concerns among regulators and the F.D.A.’s outside experts about the administration’s strategy.

The F.D.A. is also expected soon to tackle the question of whether to authorize coronavirus vaccines on an emergency basis for children under 12.

Last week, the agency fully approved the Pfizer-BioNTech vaccine for people 16 and older, a major decision that spurred a series of vaccine mandates at corporations, universities, hospitals and elsewhere.

That decision and a host of others fell to teams led by Dr. Gruber and Dr. Krause, working under Dr. Marks.

The F.D.A. reviews data from vaccine manufacturers on safety and efficacy, and sometimes makes decisions with input from the outside advisory committee of vaccine experts. The agency’s decisions are followed by recommendations from the Centers for Disease Control and Prevention, after it hears from its own outside panel of experts.

Both Dr. Gruber and Dr. Krause have been at the agency for 30 years and have long experience reviewing vaccines, including for Ebola. The office they lead evaluates annual flu vaccines, including which strains each year’s version targets, and it had a central role in the F.D.A.’s authorization of three coronavirus vaccines, which also include a single-dose shot from Johnson & Johnson.

Their office also guides manufacturers on what kinds of studies they need to conduct to evaluate new vaccines, then reviews the data on them. The F.D.A. came under enormous pressure last fall by Trump administration officials to water down or scuttle standards it had set for vaccine emergency use authorizations, but prevailed in publishing the guidelines. Dr. Stephen M. Hahn, the F.D.A. commissioner under President Donald J. Trump, said on Tuesday that Dr. Gruber and Dr. Krause “stuck together and marshaled amazing resources and got the authorizations done in record time.”

“They set the gold standard” for vaccine reviews, said Dr. Luciana Borio, the former acting chief scientist at the agency under President Barack Obama. During the pandemic, she added, “they put their heads down and organized their team to do this work under tremendous pressure, but do it in a rigorous, expedited and flexible form.”