The FDA’s action also may spur more vaccine mandates by companies, universities and local governments. This month New York City, New Orleans and San Francisco all imposed proof-of-vaccination requirements at restaurants, bars and other indoor venues. At the federal level, President Joe Biden is requiring government workers to sign forms attesting that they’ve been vaccinated or else submit to regular testing and other requirements.

Anxious Americans increasingly are on board: Close to 6 in 10 favor requiring people to be fully vaccinated to travel on airplanes or attend crowded public events, according to a recent poll by The Associated Press-NORC Center for Public Affairs Research.

“Mandating becomes much easier when you have full approval,” said Dr. Carlos del Rio of Emory University. “I think a lot of businesses have been waiting for it.”

The FDA, like regulators in Europe and much of the world, initially allowed emergency use of Pfizer’s vaccine based on a study that tracked 44,000 people 16 and older for at least two months — the time period when serious side effects typically arise.

That’s shorter than the six months of safety data normally required for full approval. So Pfizer kept that study going, and the FDA also examined real-world safety evidence in deciding to fully license the vaccine for people 16 and older, those studied the longest. Pfizer’s shot still has emergency authorization for 12- to 15-year-olds.

Even after hundreds of millions of shots, serious side effects — such as chest pain and heart inflammation in teens and young adults — remain exceedingly rare, the FDA said.

As for effectiveness, six-month tracking of Pfizer’s original study showed the vaccine remained 97% protective against severe COVID-19. Protection against milder infection waned slightly, from a peak of 96% two months after the second dose to 84% by six months.

Those data came before the extra-contagious delta variant began spreading, but other data from the Centers for Disease Control and Prevention shows the vaccine is still doing a good job preventing severe disease caused by that mutant.

As for all the talk about booster doses, the FDA’s licensure doesn’t cover those. The agency will decide that separately.

The FDA already is allowing emergency use of a third dose of either the Pfizer or Moderna vaccine for people with severely weakened immune systems, such as organ transplant recipients who don’t respond as strongly to the usual two shots. For everyone else who got those vaccinations, the Biden administration is planning ahead for booster starting in the fall — if the FDA and CDC agree.

Also still to be decided is vaccination of children under 12. Both Pfizer and Moderna are studying youngsters, with data expected in the fall.7