The U.S. gave full approval for use of the Covid-19 vaccine from Pfizer Inc. PFE 2.48% and partner BioNTech SE BNTX 9.58% Monday, a move quickly followed by announcements from the Pentagon, the New York City school district and others that they would begin requiring vaccinations.

The Food and Drug Administration’s approval was seen by public health officials as a key step to convince hesitant individuals to get the shot and to encourage employers to mandate it.

“Today I’m calling on more companies in the private sector to step up with vaccine requirements that will reach millions more people,” President Biden said. “I call on you to do that—require it.”

The Pfizer-BioNTech vaccine was cleared by regulators last year on an emergency-use basis, as were subsequent clearances for Moderna Inc. MRNA 7.55% and Johnson & Johnson JNJ -0.43% vaccines.

A weekly email that will help you set and accomplish your personal goals, with tips and conversations to improve your health, career, relationships and downtime.Following Monday’s action by the FDA, the Pentagon said it would require all military service members to receive a Covid-19 vaccine. New York City Mayor Bill de Blasio said the city’s Department of Education will require vaccinations for all employees, and New Jersey Gov. Phil Murphy said the shots will be mandated for school employees.

The Pfizer-BioNTech vaccine was first cleared in December by the FDA on an emergency-use basis for people 16 years and older after the drugmakers showed it to be highly effective at preventing symptomatic Covid-19. The two-dose shot, resulting from the fastest vaccine development ever in the West, has since become the most received Covid-19 vaccine in the U.S.

Of the three authorized vaccines in the U.S., only Pfizer had submitted all the required information to the FDA for full approval, according to the companies, and analysts expected it to be the first to receive clearance.

Moderna, whose authorized two-dose shot uses similar mRNA technology as the Pfizer-BioNTech vaccine, has said it is still completing rolling data submissions. Johnson & Johnson, whose shot was authorized in February, has said it plans to file for full approval later this year.

The FDA’s action Monday came as U.S. hospitals are seeing a surge in cases tied to the contagious Delta variant, and as the government weighs when vaccinated adults should receive additional doses, putting pressure on the agency to act quickly.

The FDA said its review found the vaccine to be safe and effective in preventing Covid-19 as well as severe disease, hospitalization and death. The most common side effects by clinical trial participants who received the vaccine included fatigue, headache, joint pain, chills and fever.

“We have not lost sight that the Covid-19 public health crisis continues in the U.S. and that the public is counting on safe and effective vaccines,” said Peter Marks, director of FDA’s Center for Biologics Evaluation and Research. “The public and medical community can be confident that although we approved this vaccine expeditiously, it was fully in keeping with our existing high standards for vaccines in the U.S.”

The Pfizer-BioNTech shot was authorized for children as young as 12 years in May. Pfizer plans to request full approval for that group once it has collected and analyzed six months of safety data from clinical-trial subjects, according to the company.

The vaccine is now eligible for off-label prescriptions—or use beyond the approved populations. That could include booster doses, according to the FDA. Prescribing the vaccine off label for children wouldn’t be appropriate as there is no data on proper dosing or safety in youth, said acting FDA Commissioner Janet Woodcock.

“That would be a great concern that people would vaccinate children because we don’t have the proper dose or safety data,” she said. “We need to get the information and data on uses on younger children.”

After regulators approve a medical product, physicians often use off-label prescribing. Dr. Woodcock said, however, this is a different situation because Covid-19 vaccination providers have agreed with the Centers for Disease Control and Prevention to adhere to certain conditions, including those that cover the vaccines.