CDC updates guidance, recommends vaccinated people wear masks indoors in certain areas

To prevent further spread of the Delta variant, the US Centers for Disease Control and Prevention updated its mask guidance on Tuesday 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.

"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 told a media briefing on Tuesday.

"This new science is...