Two studies that have not yet been peer reviewed indicate increased protection against the infectious omicron variant.
CDC Director Rochelle Walensky also endorsed a mix-and-match approach to boosters that would be flexible for patients and health care providers.
The U.S. donation from its domestic supplies comes on top of the 50 million doses previously donated to Africa, which world health officials say is 500 million doses short of its goal.
The COVID-19 vaccines continue to provide powerful protection, even against the delta variant, the CDC said. It also found that vaccinated people were 10 times less likely to be hospitalized.
Federal regulators say they have confidence the vaccine is safe and effective at preventing COVID-19 and the benefits outweigh the risks.
While emphasizing that the risk is low, the health agency said there should be a warning about the rare condition included in the product information for the vaccine.
An expert advisory committee to the CDC decided it needed more time to consider whether to recommend the restart administration of the COVID-19 vaccine made by Johnson & Johnson.
Soon after U.S. regulators paused the use of the J&J single-dose vaccine, health authorities in many European countries and in South Africa announced that they were also putting it on hold.
As the new Johnson & Johnson COVID-19 vaccine rolls out, the health care community is trying to ward off misconceptions about it. The vaccine's one-shot feature may be what wins many over.
Catholic bishops say the Pfizer and Moderna vaccines did not use abortion-derived fetal cell lines, but that the Johnson & Johnson vaccine is acceptable, if it's the only available option.
Johnson & Johnson has started shipping its first vaccine doses across the U.S., adding a third vaccine to the country's arsenal as public health officials warn of an uptick in cases.
The U.S. Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee are discussing on Friday the newest vaccine against COVID-19 for emergency use authorization.
"We've now purchased enough vaccine supplies to vaccinate all Americans," Biden said on Thursday. "Now we're working to get those vaccines into the arms of millions of people."
A study raised concerns about its effectiveness against the coronavirus variant sweeping through the country — although the data is too preliminary for definitive conclusions.