>>13535192We have to fill in a lot of blanks there, but anyway, if both become exposed to the virus somehow, the vaccinated person will have slightly better protection against minor symptomatic infection and 75-100% protection against severe illness or death, depending on the time since vaccination, which vaccine was taken, and the viral strain involved. Realistically, eliminating overly optimistic and overly pessimistic outliers, we see that the vast majority of studies hit the 80-95% range.
