Delta variant of the coronavirus is as contagious as chickenpox, probably causes more severe disease than past strains, and breakthrough cases in vaccinated individuals may be as transmissible as unvaccinated cases, according to a leaked US government document.
The internal slide presentation produced by the Centers for Disease Control and Prevention (CDC) stresses that "the war has changed" as a result of Delta.
It was first reported by The Washington Post and has been verified by AFP. CDC director Rochelle Walenksy cited data from the presentation this week to justify a return to masks for vaccinated people in high-risk areas.