A doctor injecting a senior with a vaccine booster shot

The Food and Drug Administration has authorized new, bivalent versions of Pfizer’s and Moderna’s COVID-19 vaccines to be used as booster shots. At the same time, the original versions of these drugmakers’ mRNA COVID-19 vaccines are no longer authorized as booster doses.

Doses of the updated booster vaccines are expected to be available to the public within days. As bivalent vaccines, they target the original form of SARS-CoV-2 as well the omicron strains currently causing most infections in the United States, the agency announced Thursday. 

The authorization nudges clinicians to edit their booster protocol. The Pfizer and Moderna original vaccines are no longer authorized as a booster option, although they may still be used as a primary series, the agency said. The newly cleared bivalent boosters are meant to be used as a single booster dose at least two months following primary or booster vaccination. 

Federal health officials encouraged development of the updated boosters this year, as the efficacy of current vaccines waned in the face of newer and highly transmissible BA.5 and BA.4 omicron variants. The FDA’s vaccine advisers in June overwhelmingly voted to recommend that stronger vaccines be used to thwart an expected surge of infections in the fall and winter.


Officials made a point to assure the public that the speedily authorized bivalent COVID-19 vaccines meet the FDA’s safety, effectiveness and manufacturing quality standards for emergency use authorization.

“The FDA has extensive experience with strain changes for annual influenza vaccines. We are confident in the evidence supporting these authorizations,” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research.

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