To prevent further spread of the Delta variant, the US Centers for Disease Control and Prevention updated its mask guidance on July 27 to recommend that fully vaccinated people wear masks indoors when in areas with "substantial" and "high" transmission of COVID-19, which includes nearly two-thirds of all US counties, CNN.com reported.
"In recent days I have seen new scientific data from recent outbreak investigations showing that the Delta variant behaves uniquely differently from past strains of the virus that cause COVID-19," CDC Director Dr. Rochelle Walensky said at a media briefing.
Currently, fully vaccinated people still play a small role in transmission and breakthrough infections are rare.
When the CDC previously revised its guidance on May 13 for vaccinated people to unmask, Delta only represented 1% of reported infections. Now, according to the CDC, it represents at least 83% of cases.
Meanwhile, the guidance for unvaccinated people throughout the country remains the same: Continue masking until they are fully vaccinated.
