A healthcare worker administers a third dose of the Pfizer-BioNTech Covid-19 vaccine at a senior living facility in Worcester, Pennsylvania on August 25.
A healthcare worker administers a third dose of the Pfizer-BioNTech Covid-19 vaccine at a senior living facility in Worcester, Pennsylvania on August 25. (Hannah Beier/Bloomberg/Getty Images)

Vaccine advisers to the US Food and Drug Administration voted unanimously Friday to recommend emergency use authorization of a booster dose of Pfizer’s vaccine six months after full vaccination in people 65 and older and those at high risk of severe Covid-19.

Members of the FDA’s Vaccines and Related Biological Products Advisory Committee had rejected a broader application – to approve the use of booster doses of Pfizer’s vaccines in everyone 16 and older six months after they are fully vaccinated.

So the FDA offered a revised question to vote on.

Members of the committee expressed doubts about the safety of a booster dose in younger adults and teens, and complained about the lack of data about the safety and long term efficacy of a booster dose.

Remember: The meeting and vote is just the start of the process. It’s the US Centers for Disease Control and Prevention who will decide whether or not they should be used. After the FDA advisory committee makes its recommendation, the FDA makes the decision about whether to approve the booster dose.

The CDC has scheduled a meeting of its vaccine advisers for Sept. 22 and 23 — and CDC must give its stamp of approval for any booster doses to be officially given.

In a letter sent Thursday and obtained by CNN, the CDC urged local and state health officials to wait to administer boosters until both agencies had signed off.

Biden administration officials have previously announced a plan to begin administering booster doses to the general population during the week of Sept. 20, pending signoff from the FDA and CDC.

Where things stand now on vaccines and boosters: Third doses are already approved for certain immunocompromised people, but not for the general public.

Pfizer received full approval for its vaccine from the FDA, so the request to add a booster dose is a supplement to that approval. Pfizer — and other researchers — say their studies show people develop strong immunity after two doses of vaccine, but that levels of antibodies start to drop after a few months

The FDA noted in its briefing documents that Pfizer’s vaccine — as well as vaccines made by Moderna and Johnson & Johnson — still provide strong protection against severe disease, hospitalization and death, even if antibodies do wane over time.

CNN’s Jamie Gumbrecht and Jacqueline Howard contributed reporting to this post.