Immunity is indeed not binary. There's sterilizing vs non-sterilizing immunity, for instance, sterilizing immunity meaning that the pathogen is purged before in

Immunity is indeed not binary. There's sterilizing vs non-sterilizing immunity, for instance, sterilizing immunity meaning that the pathogen is purged before infecting cells (emphasis mine): > Without a strong mucosal response, injected vaccines may be less likely to produce so-called sterilizing immunity, a phenomenon in which a pathogen is purged from the body before it’s able to infect cells, Dr. Durbin said. Vaccinated people might be protected from severe disease, but could still be infected, experience mild symptoms and occasionally pass small quantities of the germ onto others. https://www.nytimes.com/2020/07/14/health/coronavirus-nasal-vaccines.html https://www.nytimes.com/2020/07/14/health/coronavirus-nasal-...