Evaluating the Effectiveness of mRNA-1273.815 Against COVID-19 Hospitalization Among Adults Aged ≥ 18 Years in the United States
Amanda Wilson, Neloufar Rahai, Ekkehard Beck, Elisha Beebe, B. Conroy, Daina B. Esposito, Priya Govil, Hagit Kopel, Tianyi Lu, James A. Mansi, Morgan A. Marks, Katherine E. Mues, Rohan Shah, Michelle Skornicki, Tianyu Sun, Astra Toyip, Mitra Yousefi, David Martin, Andre B. Araujo
Abstract
INTRODUCTION: In September 2023 the Food and Drug Administration (FDA) approved an updated mRNA COVID-19 vaccine targeting the XBB.1.5 sublineage. This study evaluates the effectiveness of mRNA-1273.815, a 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine in preventing COVID-19-related hospitalizations and medically attended COVID-19 in US adults aged ≥ 18 years. METHODS: This observational, matched cohort study used medical and pharmacy claims data from HealthVerity. Adults vaccinated with mRNA-1273.815 between September 12, 2023, and December 31, 2023, were followed through January 26, 2024. Vaccinated individuals were matched with individuals unvaccinated with any 2023-2024 COVID-19 vaccine on demographic and clinical characteristics. The primary and secondary outcomes were COVID-19 hospitalization and medically attended COVID-19, respectively. Inverse probability of treatment weighting and Cox proportional hazards regression were utilized to estimate vaccine effectiveness (VE). RESULTS: The study included 1,272,161 vaccinated individuals matched 1:1 with unvaccinated individuals, with a maximum follow-up of 128 (median 84) days. The VE against COVID-19 hospitalization was 51% (95% confidence interval [CI]: 48-54%). Subgroup analyses showed a VE of 56% (95% CI 51-61%) among adults ≥ 65 years and 46% (95% CI 39-52%) in immunocompromised adults. For medically attended COVID-19, the VE was 25% (95% CI 24-27%). Time-varying analyses showed that while VE declined over time, VE remained significant. CONCLUSION: During the 2023-2024 respiratory season, the mRNA-1273.815 vaccine significantly protected against COVID-19-related hospitalizations and medically attended COVID-19 across diverse adult populations and demonstrated durability of the effect. These results support the continued use of updated COVID-19 vaccines to mitigate severe outcomes and maintain public health safety.