mRNA vaccines highly effective at preventing death, less at preventing infection

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.»

Vaccines literally require infection for the vaccine to have a chance to work to keep you from getting sick. More precisely, while the the vaccines do reduce the severity and duration of infection enough to greatly improve chances of survival, they do not do so enough as to render the vaccinated non-contagious. This isn't unusual. We see the same thing with influenza vaccines, but also the mumps vaccine and probably others. I know this seems pedantic but a lot of people seem to be operating under a misconception that the vaccines somehow prevent infection like a plastic barrier, and headlines like this no doubt contribute to the confusion.

Musing: will there be a vaccine or treatment that prevents infection, either in the infected or the infectee, as a preventative measure?