Millions of Americans may soon receive a third dose of the Pfizer-BioNTech COVID-19 vaccine.

On Wednesday, the Food and Drug Administration announced it had approved a booster shot for individuals 65 and older, as well as any other adult who are at high risk of suffering severe COVID complications. The news comes just days after an independent advisory panel voted against a broad rollout of a booster for Americans ages 16 and above. The agency has also authorized a booster for individuals whose occupations put them at greater risk of exposure.

“Today’s action demonstrates that science and the currently available data continue to guide the FDA’s decision-making for COVID-19 vaccines during this pandemic ...” acting FDA Commissioner Dr. Janet Woodcock said in a statement. “After considering the totality of the available scientific evidence and the deliberations of our advisory committee of independent, external experts, the FDA amended the EUA for the Pfizer-BioNTech COVID-19 Vaccine to allow for a booster dose in certain populations such as health care workers, teachers and day care staff, grocery workers and those in homeless shelters or prisons, among others.”

She continued: “This pandemic is dynamic and evolving, with new data about vaccine safety and effectiveness becoming available every day. As we learn more about the safety and effectiveness of COVID-19 vaccines, including the use of a booster dose, we will continue to evaluate the rapidly changing science and keep the public informed.”

The FDA states eligible Americans may receive a booster after six months from their second dose. The agency says it expects to share additional information regarding the effectiveness and safety of a third dose in the upcoming weeks. The Centers for Disease Control and Prevention is also set to review the FDA’s decision on Thursday, and will likely issue guidance on the booster policy.