New US mask guidance prompted by evidence vaccinated can spread Delta

CDC director Rochelle Walensky cites new science'

People with outbreak infections can pass on virus

The director of the Centers for Disease Control and Protection spoke on Wednesday about evidence that vaccinated people can spread the Covid-19 Delta variant to others, after the nation's top health agency expanded on its new guidance that fully vaccinated Americans wear masks indoors in certain places.

Rochelle Walensky said new science" observed in recent days demonstrated that new variants of the coronavirus were transmissible by people who have been fully vaccinated in some cases.