WASHINGTON D.C.
— Vaccinated people who become infected can spread the delta variant, according to the U.S. Centers for Disease Control and Prevention, whose research included a detailed study of a COVID-19 outbreak that started July 3 in a town in Massachusetts.
The study initially involved 469 cases, three quarters of whom had been fully vaccinated, with 90 percent of sequenced samples found to be carrying the delta variant.
Crucially, it found the viral loads of the still-rare people who are both vaccinated and infected with delta was similar to unvaccinated people.
This means the number of virus particles in their airways was almost the same, and the CDC says that helps determine the risk of transmission.