Currently authorized vaccines in the United States are highly effective at protecting vaccinated people against symptomatic and severe COVID-19. Fully vaccinated people are less likely to become infected and, if infected, to develop symptoms of COVID-19. They are at substantially reduced risk of severe illness and death from COVID-19 compared with unvaccinated people.
Infections in fully vaccinated people (“breakthrough” infections) happen in only a small proportion of people who are fully vaccinated, even with the Delta variant. Moreover, when these infections occur among vaccinated people, they tend to be mild. However, preliminary evidence suggests that fully vaccinated people who do become infected with the Delta variant can be infectious and can spread the virus to others.