Coronavirus disease 2019 (COVID-19) vaccines effectively prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related illness and death. Because COVID-19 vaccines are not 100% effective in preventing illness, certain infections among those who have been vaccinated are expected.
The involvement of vaccinated people in the transmission will be a major predictor of the pandemic’s future trajectory as global vaccination coverage rises. The extent to which vaccinated people who become infected contribute to the spread of SARS-CoV-2, including the B.1.617.2 (Delta) variant, is unknown.
