Population immunity and vaccine protection against infection

With the intense surveillance protocol, the risk of missing an asymptomatic infection was small. [...]SIREN provides robust real-world estimates of vaccine protection against infection, a crucial component to understanding how vaccination can curtail transmission. [...]a one-dose strategy might be best for averting the most deaths, but higher population immunity to quell transmission will require a full course of two doses. Presence of symptoms has a complex relationship with SARS‑CoV‑2 transmission, since asymptomatically infected people play a key role in spread.9 However, since breakthrough cases among vaccinated individuals shed virus at lower levels, they are probably less infectious than unvaccinated individuals are.3 Second, in this study population, participants who previously had COVID-19 were less likely to be vaccinated.