Key paragraph: «Our target trial emulation study in the national VA health care system among 2 099 871 persons vaccinated with mRNA COVID-19 vaccines between 11

Key paragraph: «Our target trial emulation study in the national VA health care system among 2 099 871 persons vaccinated with mRNA COVID-19 vaccines between 11 December 2020 and 25 March 2021 and matched 1:1 to unvaccinated controls estimated that VE at 7 or more days after the second vaccine dose was 69% (CI, 67% to 70%) for SARS-CoV-2 infection and 86% (CI, 82% to 89%) for SARS-CoV-2–related death during follow-up extending to 30 June 2021. Vaccine effectiveness did not decline when follow-up was extended from 31 March to 30 June 2021. Vaccine effectiveness against SARS-CoV-2 infection decreased with increasing age and comorbidity burden. This study advances our understanding of “real-world” mRNA COVID-19 VE by focusing on an older, racially and ethnically diverse, high-comorbidity population; applying target trial emulation methods that strengthen causal inferences; and examining whether VE declines over longer follow-up.»