The benefit of masking to protect others has been widely described. In this article, Gandhi et al compiled virologic and epidemiologic evidence to assess the link between mask wearing, the viral inoculum, and rates of asymptomatic SARS-CoV-2 infection. The authors note that rates of asymptomatic and mild infections have increased in settings where population-level masking has occurred; for example, a systematic review of studies before mask wearing was commonly practiced estimated the proportion of asymptomatic infection to be 15% while a later narrative review placed the proportion at 40-45%. The authors also identified examples of specific settings (a cruise ship, a hemodialysis unit, a seafood processing plant, and a chicken plant) in which individuals were exposed to the virus and masking was used; in these examples the outcomes were high rates of asymptomatic infection. The authors posit that universal masking reduces the dose of the virus for the person wearing the mask, leading to less-severe illness and potentially to increases in community-level immunity.