Real-world comparative effectiveness of a third dose of mRNA-1273 versus BNT162b2 among adults aged ≥ 65 years in the United States

To compare the real-world effectiveness of a third dose of mRNA-1273 versus a third dose of BNT162b2 against breakthrough COVID-19 hospitalizations among adults aged ≥ 65 years who completed a primary series of an mRNA-based COVID-19 vaccine (regardless of which primary series was received). This observational comparative vaccine effectiveness (VE) study was conducted using administrative claims data from the US HealthVerity database (September 22, 2021, to August 31, 2022). A third dose of mRNA-1273 versus BNT162b2 was assessed for preventing COVID-19 hospitalizations and medically attended COVID-19 among adults aged ≥ 65 years. Inverse probability of treatment weighting was applied to balance baseline characteristics between vaccine groups. Incidence rates from patient-level data and hazard ratios (HRs) with 95 % confidence intervals (CIs) using weighted Cox proportional hazards models were calculated to estimate relative VE for each outcome. Overall, 94,587 and 92,377 individuals received a third dose of mRNA-1273 and BNT162b2, respectively. Among the weighted population, the median age was 69 years (interquartile range, 66–74), 53 % were female, and 46 % were commercially insured. COVID-19 hospitalization rates per 1000 person-years (PYs) were 5.61 (95 % CI, 5.13–6.09) for mRNA-1273 and 7.06 (95 % CI, 6.54–7.57) for BNT162b2 (HR, 0.82; 0.69–0.98). Medically attended COVID-19 rates per 1000 PYs (95 % CI) were 95.05 (95 % CI, 93.03–97.06) for mRNA-1273 and 106.55 (95 % CI, 104.53–108.57) for BNT162b2 (HR, 0.93; 0.89–0.98). Results from this observational comparative VE database study provide evidence that among older adults, a third dose of mRNA-1273 was more effective in preventing breakthrough COVID-19 hospitalization and medically attended COVID-19 infection compared with a third dose of BNT162b2.