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

Introduction: 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).

Materials And Methods: 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.

Results: 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).

Conclusions: 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.