OBJECTIVES: COVID-19 is a leading cause of avoidable hospitalizations in older adults aged ≥65 in the US and these account for the majority of COVID-19 associated direct medical costs. The objective of this study was to compare the real-world effectiveness of a first original booster dose of mRNA-1273 versus BNT162b2. The current analysis focused on the risk of hospitalization and associated expenditures in non-immunocompromised Medicare fee-for-service (FFS) beneficiaries aged ≥65.

METHODS: This retrospective cohort study used Medicare FFS claims data from October 2020 through August 2022. Individuals who received a booster dose of mRNA-1273 (2.4 million) or BNT162b2 (1.6 million) after ≥1 dose of mRNA-based primary vaccine series were followed from 14 days after index until receipt of an additional booster dose, outcome occurrence, end of continuous enrollment, or end of study period. Inverse probability of treatment weighting (IPTW) was applied to adjust for baseline confounding. Comparative vaccine effectiveness against COVID-19 hospitalization (principal or secondary diagnosis) and differences in total expenditures during hospitalization and up to 90 days post-discharge were estimated.

RESULTS: After IPTW, individuals who received mRNA-1273 as a booster had a reduced risk of hospitalization (hazard ratio [HR] 0.789; 95% confidence interval: 0.766, 0.813) compared to BNT162b2. Differences in total expenditures during hospitalization and up to 60 days post-discharge between mRNA-1273 versus BNT162b2 recipients were -$723 (USD) or -1.8% (p=0.08), showing savings compared with BNT162b2. In sensitivity analysis, differences in total expenditures during stay up to 30 days post-discharge were -$678 (-2.4%, p=0.02); up to 90 days post-discharge were $10 (0.0%, p=0.99); and for hospitalizations with COVID-19 as principal diagnosis (up to 60 days post-discharge) were -$2,224 (-6.3%, p<0.001), respectively.

CONCLUSIONS: mRNA-1273 administered as a first booster was more effective than BNT162b2 in preventing COVID-19 hospitalizations and associated with lower medium-term Medicare expenditures for those hospitalized.