These IVY Network investigators from 18 US states sought to define vaccine effectiveness of the bivalent COVID-19 vaccine against hospitalization in elderly patients. Between September 8 and November 30, 2022, 798 patients hospitalized with a COVID-like illness were enrolled in this test-negative analysis. Among immunocompetent adults aged ≥65 years, a bivalent booster dose received after ≥2 monovalent mRNA doses provided good protection (73%) against COVID-19-associated hospitalization during this period of Omicron BA.5 or BQ.1/BQ.1.1 predominance. Compared to unvaccinated patients, the bivalent vaccine effectiveness was 84%. Substantial additional protection from a bivalent booster dose was observed when compared with remote monovalent-only mRNA vaccination.

https://www.cdc.gov/mmwr/volumes/71/wr/mm715152e2.htm?s_cid=mm715152e2_w