Scientists studying a large COVID-19 outbreak in Massachusetts concluded that vaccinated people who got so-called breakthrough infections carried about the same amount of the coronavirus as those who did not get the shots, which is a dispiriting setback for the nation’s efforts to eradicate the virus.
Health officials on Friday released details of that research, which was key in this week’s decision by the Centers for Disease Control and Prevention to recommend that vaccinated people return to wearing masks indoors in parts of the U.S. where the delta variant is fueling infection surges. The authors said the findings suggest the CDC’s mask guidance should be expanded to include the entire country, even outside of hot spots.
The results have the potential to change how we think about how illness spreads in the future. Previously, it was assumed that vaccinated persons who were infected had low amounts of virus and were unlikely to spread it to others. However, fresh evidence suggests that this is not the case with the delta form.
