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 variant was also more likely to break through protections afforded by the vaccines, the report said, adding that the agency's reverse course on masking guidelines for fully vaccinated Americans on Tuesday was based on this document.
However, CDC's figures show the vaccines are highly effective in preventing serious illness, hospitalisation and death in vaccinated people, the report said, citing experts.
New research showed the vaccinated people infected with the Delta variant carried tremendous amounts of the virus in the nose and throat, CDC Director Rochelle Walensky told the Times.
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.
Reuters.