Dr. Hahn told the newspaper that a vaccine developer could apply for approval before the end of Phase 3 clinical trials, which are the largest and most rigorous, but the agency would make "a science, medicine, data decision" and possibly issue an emergency would be permission to use for particularly vulnerable groups instead of a blanket permit.
"This will not be a political decision," he said.
Dr. Hahn's comments, published online by the Financial Times on Sunday, weren't his first indication that the agency could expedite a vaccine in the right circumstances, which wouldn't conflict with the agency's standard protocols. However, the interview took place at the end of a particularly turbulent week for the F.D.A.
Last weekend, after President Trump criticized the agency for moving too slowly to develop vaccines and treatments and accused them of being part of the "deep state", Dr. Hahn with Mr Trump at a news conference where they made false claims that overstated the benefits of plasma treatments for Covid-19, which is sparking a wave of scientific disbelief and criticism.
Dr. Hahn later corrected the misleading claims. On Thursday, the Department of Health and Human Services, the parent agency of the FDA, announced the contract of a public relations consultant, Dr. Hahn had advised the correction to be issued, and the FDA chief spokeswoman, who was on the job for only 11 days, was removed from her position.
Last week, The Times reported that Treasury Secretary Steven Mnuchin and White House Chief of Staff Mark Meadows told Spokeswoman Nancy Pelosi and Democratic leader Senator Chuck Schumer on July 30 that a vaccine would likely get emergency approval before the end of clinical Phase 3 trials in the US, possibly as early as late September.
The report was based on information from two people who were briefed on the discussion, saying that Mr Meadows said it would most likely be the one being developed by AstraZeneca and Oxford University, which is currently in the UK, Brazil Phase 2 and going through phase 3 trials and South Africa. However, senior administration officials denied the account, saying that Mr Meadows and Mr Mnuchin were either misrepresented or misunderstood.
Last week, Dr. Anthony S. Fauci, the nation's leading infectious disease expert, told The Times of London that three vaccine candidates focused on Operation Warp Speed, the White House's effort to accelerate vaccine development, would be up for testing by November or December achieving was "a sure thing". He also said it was "possible that we will get an answer beforehand".