The Food and Drug Administration on Friday authorized Pfizer and Moderna COVID-19 vaccine booster shots for all American adults ages 18 and up in the hope of providing Americans extra protection against the virus ahead of a potential winter surge.

Later in the day, Centers for Disease Control and Prevention vaccine advisers voted to recommend administering booster shots.

Acting FDA Commissioner Janet Woodcock called the emergency authorization a “timely public health decision,” considering waning vaccine efficacy and the coming winter months that often bring people together indoors where the virus spreads more easily.

“Streamlining the eligibility criteria and making booster doses available to all individuals 18 years of age and older will also help to eliminate confusion about who may receive a booster dose and ensure booster doses are available to all who may need one,” FDA’s Center for Biologics Evaluation and Research Director Peter Marks noted.

Booster shots are already available to many Americans. In recent weeks, Kentucky, New York City, California, Colorado, Connecticut and New Mexico moved ahead with booster shots for all adults without the administration’s blessing.

The Biden administration previously authorized COVID-19 booster shots for older adults and people at high risk because of their jobs, health or living conditions, as well as all Americans who received the Johnson & Johnson vaccine. This latest authorization covers the few people left out of those categories.

The FDA did not consult its vaccine advisers, as it usually does. CDC vaccine advisers were set to meet at noon Friday to discuss recommendations for booster distribution and administration, and once CDC Director Rochelle Walensky signs off on that, providers can start putting shots in arms.

COVID-19 breakthrough cases are becoming more common as vaccine efficacy wanes over time, yet severe disease, hospitalization and death are still rare for vaccinated and otherwise healthy adults.

Roughly 1,000 Americans are still dying of COVID-19 every day, and the U.S. is averaging 83,600 cases per day. But much of the current COVID-19 spread is fueled by unvaccinated individuals, not vaccinated people in need of a booster shot.

Still, many public health officials worry that the coming holiday season, combined with colder temperatures, more time spent indoors and loosening prevention policies nationwide, could cause more cases of COVID-19.

FDA vaccine advisers twice voted in past meetings against opening up booster shots to young and healthy adults. They argued that the healthiest members of society are already unlikely to face severe outcomes from COVID-19, and a booster shot would be superfluous. This week, public health officials indicated it is necessary.

“I don’t know of any other vaccine that we only worry about keeping people out of the hospital. I think an important thing is to prevent people from getting symptomatic disease,” White House Chief Medical Adviser Anthony Fauci said Wednesday.

Pfizer released data in October demonstrating that a booster dose administered to individuals who received the Pfizer-BioNTech primary two-dose vaccine had a relative vaccine efficacy of 95 percent after the booster shot.

“As we near the two-year mark in our fight against COVID-19, we have reached another critical milestone with the expanded authorization of a booster dose of our COVID-19 vaccine in individuals 18 years and older,” said Pfizer Chairman and Chief Executive Officer Albert Bourla. “With boosters, more adults will now have the opportunity to help preserve a high-level of protection against this disease.”