The current surge in infections with the SARS-CoV-2 Delta variant has made it clear to health care workers and the public alike that fully vaccinated people remain at risk for SARS-CoV-2 infections. It is also apparent that breakthrough infections in fully vaccinated people can sometimes be serious. As of October 21, 2021, for example, 35% of the 519 patients hospitalized with COVID-19 in Massachusetts had been fully vaccinated. Furthermore, multiple reports have documented that if fully vaccinated individuals do become infected, their viral loads may be as high as the levels seen in unvaccinated individuals. In July 2021, these observations led the US Centers for Disease Control and Prevention to modify its guidance for fully vaccinated people, advising that those in communities with substantial or high SARS-CoV-2 transmission rates should wear masks indoors regardless of their vaccination status. A wealth of new data has since emerged that is helping to deepen understanding of the frequency, severity, and importance of breakthrough infections in fully vaccinated individuals.
Source: JAMA Online First