CDC to update mask guidance for vaccinated people

The Centers for Disease Control and Prevention is expected to revise its mask guidance Tuesday afternoon, saying fully vaccinated Americans should wear masks indoors in communities where there is substantial or high transmission, according to a federal official. 

The announcement is expected to come at a 3 p.m. briefing. It isn't yet clear how substantial or high transmission will be determined.  The change comes as the Delta variant sweeps across the country, although health officials still insist the approved vaccines give strong protection against the most serious effects of the virus. Up to this point, federal health officials had not made any recommended changes for fully vaccinated people since announcing that fully vaccinated people do not need to wear masks in most indoor settings.