Covid-19 vaccines work 'exceptionally well' against severe illness and death but no longer prevent transmission, CDC chief says

Covid-19 vaccines no longer prevent transmission, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said Thursday. 'Our vaccines are working exceptionally well,' Walensky told CNN's Wolf Blitzer. 'They continue to work well for Delta, with regard to severe illness and death -- they prevent it. But what they can't do anymore is prevent transmission.' That's why the CDC changed its guidance last week and is now recommending even vaccinated people wear masks indoors again, Walensky said.