Rochelle Walensky signed off on a series of recommendations from a panel of advisers hours after the advisers said boosters for the Pfizer-BioNTech COVID-19 vaccine should be offered to people 65 and older, nursing home residents and those ages 50 to 64 who have risky underlying health problems.

People who have gotten two shots and decide not to get a third will still be considered fully vaccinated, the CDC said.

The evidence is clear that most vaccinated Americans remain well protected by the shots they already received, committee members and CDC officials said.

More than 90% of those currently hospitalized with COVID-19 have not been vaccinated and the best way to combat the current pandemic is to give initial shots to those who have not had any, they said.

Lab research and data from Israel, where booster shots were made widely available this summer, suggests protection against COVID-19 infection begins to wane about six months after initial shots, though hospitalization for vaccinated people remains rare.

A booster from Pfizer-BioNTech would be the same dose at the same vaccine as the previous two doses.

Not enough research has been completed to say that it's safe to get initial doses of one vaccine and then switch to another, Dr.

Moderna has requested authorization for a lower dose of its initial vaccine to be used as a booster, which the FDA is currently considering and which could become available for boosters in coming weeks?

Tracking COVID-19 vaccine distribution by state: How many people have been vaccinated in the U.S..

Francis Collins said he had gotten the Moderna vaccine and is waiting for results of an NIH trial testing whether it's safe to boost people with a different vaccine than they got the first time.

In its other decisions Thursday, the ACIP panel voted 13-2 in favor of booster doses at least six months after initial shots for people ages 50-64 who have underlying medical issues that put them at higher risk for severe COVID-19.

They were more divided on whether to support boosters for younger people, but decided 9-6 to recommend that people ages 18-49 with underlying medical issues get a booster shot at least six months after their initial doses.

"In my opinion, there's little marginal benefit to making this booster dose available at this time," said Dr.

But many vaccinated people are ready for a booster dose.

People who are unvaccinated, though, said they would be more likely to reject vaccination if they knew that booster doses were available.

Although the committee recommended boosters at least six months after initial doses, that doesn't mean people need to run to get a third shot six months and one day after their first two, said Rachael Piltch-Loeb, a biostatistician at the Harvard T.