Vaccine efficacy and duration of protection

Why are some vaccinated people getting sick with COVID-19 and in some cases being hospitalized?


Most people who get severe COVID-19 disease are unvaccinated. The main aim of COVID-19 vaccines is to protect against severe illness, hospitalizations and deaths, and they do this very well. They also reduce, but cannot eliminate the risk of infection with the virus that causes COVID-19. Since vaccines are not 100% effective at preventing infection, some people who are fully vaccinated will still get COVID-19. In most cases, these so-called ‘breakthrough’ infections among people who are fully vaccinated cause mild symptoms. There are increasing data demonstrating a stark distinction in the case outcomes of the unvaccinated compared to the vaccinated. Infection and hospitalization rates for people who are vaccinated are much lower than for people who are not vaccinated.