LATEBREAKER
Infectious Disease
Is a COVID-19 booster dose still helpful? Association between the COVID-19 vaccine and risk of COVID-19 hospitalization during Omicron Margaret Lind* Margaret Lind Matt DT Hitchings Sameer Pandya Derek AT Cummings Wade Schulz Albert I Ko
Background: COVID-19 severity diminished with the emergence of the Omicron variant. As a result, the protective effect of COVID-19 vaccine booster doses against severe disease remains unclear. Here, we examine the associations between receiving a COVID-19 booster dose and the risk of COVID-19 related hospitalization during the Omicron predominant period (12/13/2021-4/30/2023).
Methods: We performed a cohort study of people within a large US health system who completed their primary COVID-19 vaccine series. We compared the risk of COVID-19 related hospitalization between booster-eligible people (180+ days since last dose) to those recently boosted using a Poisson regression. Age stratified analyses were performed and marginal effects were estimated using G-computation.
Results: The 768,524 people who were booster-eligible or recently boosted during the study period experienced 5,324 COVID-19 related hospitalizations. Compared to booster-eligible people, people boosted in the last 14-59 days were significantly less likely to have a COVID-19 related hospitalization (Vaccine Effectiveness: 45.4% [40.8-49.7%]; Risk Difference [RD]: -8.4 [-8.5, -8.1] events/1000 person-months [pms]). The risk of hospitalization among booster-eligible people was highest for people aged ≥60 years (35.6 events/1000pms). The relative risk reduction in the 14-59 days following booster dose receipt was highest for people aged <30 years but the absolute reduction was greatest for people aged ≥60 years (RD; -13.2 [-13.3, -12.7]; Figure1).
Discussion: Booster dose receipt reduced the number of hospitalizations among people vaccinated in the last 14-59 days by ~8 events per 1000pms, corresponding to a 52% risk reduction. While there was a significant reduction for all age groups, people aged ≥60 years had the greatest underlying risk and largest absolute reduction. These findings suggest that booster doses provide protection regardless of age but that the benefit is greater for older people.
