Dr. Peter Marks, one of the Food and Drug Administration’s highest-ranking regulators, on Monday took over the agency’s vaccines office, whose two leaders had publicly questioned whether the general population needed coronavirus booster shots.

Dr. Marks said in an email to staff that the move, which makes him acting director of the office, would allow the two — Dr. Marion Gruber, the director of the vaccines office, and Dr. Philip Krause, her deputy — to “take care of close-out activities prior to departing and help to assure a smooth transition.”

Dr. Gruber recently announced plans to retire at the end of October, and Dr. Krause in November.

Both have evaluated vaccines for decades at the agency’s Office of Vaccines Research and Review, and were said to have been upset at the Biden administration’s announcement last month that booster shots would be available to most adults by the week of Sept. 20, contingent on F.D.A. clearance.

The two regulators wrote in The Lancet earlier this month that there was no credible evidence yet in support of booster shots for the general population, and that more data and public discussion were needed. Their position was shared by many independent scientists, who have said that coronavirus vaccines continue to be powerfully protective against severe illness and hospitalization.

After a tense meeting of the F.D.A.’s vaccine advisory panel, Dr. Gruber last week signed the agency’s decision memo behind its authorization of Pfizer-BioNTech booster shots for people 65 and older, people at high risk of severe Covid-19 and others at risk of serious complications from Covid-19 whose jobs frequently expose them to the virus.

The C.D.C.’s vaccine advisory panel delivered a similar vote, but not did endorse offering boosters based on one’s job. Dr. Rochelle P. Walensky, the agency’s director, overruled the advisers and recommended shots for people based on “occupational or institutional setting.”

President Biden said last week that 60 million people would be eligible for a Pfizer-BioNTech booster over the coming months.

The F.D.A.’s vaccines office has more important decisions ahead, including whether to authorize the Pfizer-BioNTech vaccine for children ages 5 to 11 and booster shots for recipients of the Moderna and Johnson & Johnson vaccines.

As director of the F.D.A.’s Center for Biologics Evaluation and Research, Dr. Marks, a hematologist and oncologist, has supervised the vaccine office’s reviews for the entirety of the pandemic. He is credited as the architect of the Trump administration’s vaccine program, Operation Warp Speed, that developed and funded coronavirus vaccines.

But Jesse Goodman, a former chief scientist at the agency, said that Dr. Marks’s decision to take over the office was “extremely unusual and concerning.” He said that the F.D.A. needed to offer a clear explanation, or else it could “erode trust” in the agency. “This just doesn’t make sense to me,” he said.