(HealthDay News) — Millions of Americans who received the Moderna and Johnson & Johnson COVID-19 vaccines will be eligible for booster shots in the near future — and they will be able choose any vaccine for their extra dose, the U.S. Food and Drug Administration announced Wednesday.

The FDA is recommending the following protocols: People who received the Moderna vaccine can get a booster at least six months after they have completed the two-dose series if they are 65 years or older, at high risk for severe disease, or work in jobs that regularly expose them to COVID-19; anyone older than 18 years who got the single-dose Johnson & Johnson vaccine can get a booster shot two months after they got the first dose; and any person eligible for a booster vaccine can “mix and match” their extra dose, regardless of the vaccine they were initially given.

The FDA decision — which followed closely on recommendations from its expert advisory panel — is one of the last steps toward a full rollout of booster shots to eligible Americans. On Thursday, the U.S. Centers for Disease Control and Prevention Advisory Committee on Immunization Practices is expected to provide more detailed guidance, with agency director Rochelle Walensky, M.D., MPH, signing off on the new recommendations.

The guidelines for Moderna vaccine recipients eligible for a booster shot mirror those set late last month for people who got the Pfizer vaccine. One difference: The Moderna booster will be a half-dose of the original vaccine, while the Pfizer booster is a full dose, the FDA said.

The agency also authorized “mix-and-match” booster doses after reviewing clinical trial data showing that an extra shot of any vaccine will provide added protection to anyone who has developed vaccine immunity, the FDA said.

“In many ways, as we move to deal with this as an infectious disease that we have to deal with, being able to interchange these vaccines is a good thing. It’s like what we do with flu vaccine. Most people don’t know what brand flu vaccine they receive,” Peter Marks, M.D., director of the FDA Center for Biologics Evaluation and Research, said during a media briefing. “If people have concerns, they should ask their providers and there might be reasons why an individual provider might decide to recommend a different booster based on side effects that were seen [during their initial series of shots].”

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