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New Covid Boosters’ Protection Waned After Two Months, Study Says

  • Bivalent shots lowered hospitalizations, deaths among elderly
  • For chronically ill adults, boosters made little difference
A resident receives a Covid-19 booster shot at a vaccine clinic in Lansdale, Pennsylvania.

A resident receives a Covid-19 booster shot at a vaccine clinic in Lansdale, Pennsylvania.

Photographer: Hannah Beier/Bloomberg

Covid-19 bivalent boosters’ protection against death and hospitalization in elderly people began waning as soon as two months after vaccination, according to a preprint study.

The findings build on previous reports about the effectiveness of updated boosters from Moderna Inc. and Pfizer Inc., which showed the shots sharply reduced risks of severe Covid in older adults, but didn’t assess how long protection lasted. The new report, written by researchers who looked at data from a Finnish patient registry, has not yet been peer-reviewed and was published as a preprint in the server MedRxiv.