F.D.A. Authorizes Pfizer Booster Shots for Older and At-Risk Americans

WASHINGTON — After weeks of internal strife at the Food and Drug Administration, the agency on Wednesday authorized people over 65 who had received Pfizer-BioNTech’s coronavirus vaccine to get a booster shot at least six months after their second injection.

The F.D.A. also authorized booster shots for adult Pfizer-BioNTech recipients who are at high risk of becoming severely ill with Covid-19 or are at risk of serious complications from the disease due to frequent exposure to the coronavirus at their jobs.

The authorization sets up what is likely to be a staggered campaign to deliver the shots, starting with the most vulnerable Americans. It opens the way for possibly tens of millions of vaccinated people to receive boosters at pharmacies, health clinics, doctors’ offices and elsewhere.

Dr. Janet Woodcock, the acting F.D.A. commissioner, said that the authorization would allow for booster doses “in certain populations such as health care workers, teachers and day care staff, grocery workers and those in homeless shelters or prisons, among others.” Her statement suggested that agency leaders took a permissive view of the subgroups it deemed eligible for an extra injection.

Roughly 22 million Americans are at least six months past their second dose of the Pfizer-BioNTech vaccine, according to the Centers for Disease Control and Prevention. About half of them are 65 and older.

Millions of Americans who received the Moderna and Johnson & Johnson vaccines are still waiting to learn whether they, too, can get boosters. The F.D.A. is expected to take up the question of boosters for them in short order.