Data on the effectiveness of BA.4/5 bivalent vaccine stratified by age and prior infection are lacking.
This test-negative study used data from individuals ≥5 years of age testing for SARS-CoV-2 with symptoms (9/15/2022‒1/31/2023) at a large national retail pharmacy chain. The exposure was receipt of 2‒4 wild-type doses and a BNT162b2 BA.4/5 bivalent vaccine (>2 months since last wild-type dose). The outcome was a positive SARS-CoV-2 test. Absolute (vs. unvaccinated) and relative (vs. 2‒4 wild-type doses) vaccine effectiveness (VE) were calculated as (1‒adjusted odds ratio from logistic regression) x 100. VE was stratified by age and self-reported prior infection.
Overall, 307,885 SARS-CoV-2 tests were included (7,916 5‒11-year-olds, 16,329 12‒17-year-olds, and 283,640 aged ≥18 years). SARS-CoV-2 positivity was 39%; 21% were unvaccinated, 70% received 2‒4 wild-type doses with no bivalent vaccine, and 9% received a BNT162b2 BA.4/5 bivalent dose. At a median of 1‒2 months after BNT162b2 BA.4/5 bivalent vaccination, depending on age group, absolute VE ranged 22-60% and was significantly higher among those reporting prior infection (range: 55‒79%) than not (range: no protection to 50%). Relative VE ranged 31-64%.
BNT162b2 BA.4/5 bivalent showed early additional protection against Omicron-related symptomatic COVID-19, with hybrid immunity offering greater protection.

© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.