Real-World Effectiveness of a Third Dose of mRNA-1273 versus BNT162b2 on Inpatient and Medically Attended COVID-19 among Immunocompromised Adults in the United States

Recent data have shown elevated infection rates in several subpopulations at risk of SARS-CoV-2 infection and COVID-19, including immunocompromised (IC) individuals. Previous research suggests that IC persons have reduced risks of hospitalization and medically-attended COVID-19 with 2 doses of mRNA-1273 (SpikeVax; Moderna) compared to two doses of BNT162b2 (Comirnaty; Pfizer/BioNTech). The main objective of this retrospective cohort study was to compare real-world effectiveness of third doses of mRNA-1273 versus BNT162b2 at multiple time points on occurrence of COVID-19 hospitalization and medically-attended COVID-19 among IC adults in the US. The HealthVerity (HV) medical and pharmacy claims database, which contains data from >330 million patients, was the data source. Both subgroup and sensitivity analyses were conducted in addition to the core comparisons noted. In propensity score-adjusted analyses, receiving mRNA-1273 vs BNT162b2 as third dose was associated with 32% (relative risk [RR] 0.68; 95% confidence interval [CI] 0.51-0.89), 29% (0.71; 0.57-0.86), and 23% (0.77; 0.62-0.93) lower risk of COVID-19 hospitalization after 90, 180, and 270 days, respectively. Corresponding reductions in medically-attended COVID-19 were 8% (0.92; 0.86-0.98), 6% (0.94; 0.90-0.98), and 2% (0.98; 0.94-1.02), respectively. Our findings suggest a third dose of mRNA-1273 is more effective than a third dose of BNT162b2 in preventing COVID-19 hospitalization and breakthrough medically-attended COVID-19 among IC adults in the US.