Comparative effectiveness of mRNA-1273 and BNT162b2 against symptomatic SARS-CoV-2 infection

Background: mRNA coronavirus disease 2019 (COVID-19) vaccines are safe and effective, but increasing reports of breakthrough infections highlight the need to vigilantly monitor and compare the effectiveness of these vaccines. Methods: We retrospectively compared protection against symptomatic infection conferred by mRNA-1273 and BNT162b2 at Mayo Clinic sites from December 2020 to September 2021. We used a test-negative case-control design to estimate vaccine effectiveness (VE) and to compare the odds of symptomatic infection after full vaccination with mRNA-1273 versus BNT162b2, while adjusting for age, sex, race, ethnicity, geography, comorbidities, and calendar time of vaccination and testing. Findings: Both vaccines were highly effective over the study duration (VE_mRNA-1273: 84.1%, 95% confidence interval [CI]: 81.6%–86.2%; VE_BNT162b2: 75.6%, 95% CI: 72.2%–78.7%), but their effectiveness was reduced during July–September (VE_mRNA-1273: 75.6%, 95% CI: 70.1%–80%; VE_BNT162b2: 63.5%, 95% CI: 55.8%–69.9%) as compared to December–May (VE_mRNA-1273: 93.7%, 95% CI: 90.4%–95.9%; VE_BNT162b2: 85.7%, 95% CI: 81.4%–88.9%). Adjusted for demographic characteristics, clinical comorbidities, time of vaccination, and time of testing, the odds of experiencing a symptomatic breakthrough infection were lower after full vaccination with mRNA-1273 than with BNT162b2 (odds ratio: 0.60; 95% CI: 0.55–0.67). Conclusions: Both mRNA-1273 and BNT162b2 strongly protect against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. It is imperative to continue monitoring and comparing available vaccines over time and with respect to emerging variants to inform public and global health decisions. Funding: This study was funded by nference.