The Food and Drug Administration Tuesday greenlit a second booster shot of Moderna’s and Pfizer-BioNTech’s Covid-19 vaccine for people ages 50 and older, after data emerged indicating a first booster wanes in effectiveness after three to six months.

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The second booster should be administered at least four months after the first, and is the same strength as other Pfizer Covid-19 vaccine doses, though it can be administered following a first booster from any authorized manufacturer, the Food and Drug Administration said in a statement,

People 12 and older with certain kinds of immune disorders will also be eligible for a second booster dose of the Pfizer shot, the FDA said, while those 18 and older who are immunocompromised can receive another Moderna dose.

The updated emergency use authorization is based in part on real-world studies in Israel, which found a second booster improved antibody activity against delta, omicron and other coronavirus variants without revealing any new safety issues.