CDC: Delta variant as contagious as chickenpox

The Delta variant of the coronavirus is as contagious as chickenpox and could cause severe illness, according to an internal document at the United States Centers for Disease Control and Prevention (CDC), The New York Times reported. 

The variant was also more likely to break through protections afforded by the vaccines, the report said, adding that CDC's decision to reverse course on masking guidelines for fully vaccinated citizens on Tuesday is based on the document.

The agency had previously said the vaccinated did not need to wear masks indoors.

Still, the CDC's figures show that the vaccines are highly effective in preventing serious illness, hospitalisation and death in vaccinated people, according to experts quoted by the newspaper.

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 before adding that the CDC is expected to publish additional data on the variant on Friday.

CDC Director Rochelle Walensky told the Times that new research showed the vaccinated people infected with the Delta variant carried tremendous amounts of the virus in the nose and throat.

Washington has resorted to increasingly blunt methods to encourage the remaining citizens to be vaccinated, including requiring federal employees to get the jab or be subject to mandatory testing and other restrictions. On Thursday, the Biden administration called on state and local governments to offer $100 payments for newly vaccinated Americans, funded by $350bn in aid granted under the American Rescue Plan Act.