Pfizer asked federal regulators on Tuesday to authorize a booster shot of its coronavirus vaccine for 16- and 17-year-olds, according to the company’s chief executive, Albert Bourla. The request is likely to mean that several million teenagers could quickly become eligible for an additional shot.

The Food and Drug Administration is expected to act promptly on Pfizer’s request, perhaps within a week, according to people familiar with the planning.

The agency authorized the vaccine, developed with BioNTech, on an emergency basis a year ago for everyone 16 and older, fully approving it for that age group in August. But at this point, those 18 or older are eligible for booster shots.

Recipients of Pfizer and Moderna vaccines are eligible for the additional injection six months after their second shot. Those inoculated with Johnson & Johnson’s vaccine, a one-shot regimen, are eligible for a booster two months after the shot.

According to data from the Centers for Disease Control and Prevention, 2.3 million 16- and 17-year-olds received their second dose of Pfizer’s vaccine at least six months ago. By the end of the year, the number is predicted to be about three million, or 36 percent of the population in that age group.

After months of angst and division among scientific advisers, the Biden administration’s booster rollout is now in full swing. All adults became eligible for booster shots on Nov. 19, although the C.D.C. only recommended them for people over 50 as well as those 18 and older living in long-term care facilities.

On Monday, the C.D.C. altered its guidance and urged all adults to get a booster shot either six months after their second dose of Moderna’s or Pfizer’s vaccine or two months after their shot of Johnson & Johnson. President Biden described boosters Monday as part of the administration’s strategy to combat the new variant, Omicron.

More than 40 million adults have gotten an extra shot since the F.D.A. first authorized the extra injections for select population groups in late September. At least another 90 million are eligible for boosters now, according to the C.D.C.’s data.