Reuters
New York - An internal report from the US health body said the strain may cause more severe disease than all other known versions of the virus.
The US Centers for Disease Control and Prevention (CDC) has described the Delta variant of the coronavirus to be as contagious as chickenpox and could cause severe illness, the New York Times reported, citing an internal CDC document.
The report said that the agency's reverse course on masking guidelines for fully vaccinated Americans on Tuesday was based on this document.
The CDC's figures show that the vaccines are highly effective in preventing serious illness, hospitalization and death in vaccinated people, the report said, citing experts.
The Delta variant is more transmissible than the viruses that cause MERS, SARS, Ebola, the common cold, the seasonal flu and smallpox, the report said.
The immediate next step for the agency is to "acknowledge the war has changed," the report cited the document as saying.
CDC is expected to publish additional data on the variant on Friday, the NYT said.