Early study: COVID booster shot effectiveness fades over time but still effective

Study: COVID booster effectiveness wanes but remains strong NEW YORK (AP) — An early look at the performance of COVID-19 booster shots during the recent omicron wave in the U.S. hinted at a decline in effectiveness, though the shots still offered strong protection against severe illness. AP NEWS

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The report, published by the Centers for Disease Control and Prevention on Friday, is considered an early and limited look at the durability of booster protection during the omicron surge that exploded in December and January but has been fading in recent weeks. ...

...researchers also found that during the time that the omicron variant has been predominant, vaccine effectiveness against outpatient visits was 87% in people who had gotten a booster two months earlier, but to 66% at four months after. Vaccine effectiveness against hospitalization fell from 91% at two months to 78% by the fourth month.

Those results, however, were based on only a small number of patients — fewer than 200 — who had been boosted four months earlier at the time of the omicron wave. And it’s unclear if those people had gotten boosters early for medical reasons that may have made them more vulnerable to severe illness.

Effectiveness after a booster was higher last year, when the delta variant was causing most U.S. cases, the study noted....