https://medicalxpress.com/news/2020-09-mask-immunity-covid-viral-dose.html How could wearing a mask help build immunity to COVID-19? It's all about the viral dose People infected with SARS-CoV-2, the virus that causes COVID-19, can spread the virus when they speak, sing, cough, sneeze or even just breathe. Scientists think face masks help limit virus spread by protecting everyone else from the infected wearer. As a result, face maks are now mandatory in many cities, states and countries to limit the spread of COVID-19. People typically wear surgical, cloth or other face coverings that don't completely prevent the virus from infecting the wearer, though medical grade surgical masks do appear to offer more protection. Nonetheless, these don't have the same level of protection as N95 or P2 "respirator" masks worn by many health-care workers. Additionally, how we wear the mask matters, as touching it often and not completely covering the nose and mouth renders it ineffective. While these face coverings may not completely prevent us from getting infected with COVID-19, they probably reduce the number of virus particles we inhale—the "viral dose". Scientists think a lower viral dose can reduce the severity of the disease we get. Indeed, where universal face masking is implemented, a much higher proportion of new infections with COVID-19 are asymptomatic.