0834 GMT September 24, 2021
The Delta variant is much more contagious, more likely to break through protections afforded by the vaccines and may cause more severe disease than all other known versions of the virus, according to an internal presentation circulated within the U.S. Centers for Disease Control and Prevention (C.D.C.).
Rochelle P. Walensky, the director of the agency, acknowledged on Tuesday that vaccinated people with so-called breakthrough infections of the Delta variant carry just as much virus in the nose and throat as unvaccinated people, and may spread it just as readily, if less often, The New York Times reported.
But the internal document lays out a broader and even grimmer view of the variant.
The Delta variant is more transmissible than the viruses that cause MERS, SARS, Ebola, the common cold, the seasonal flu and smallpox, and it is as contagious as chickenpox, according to the document, a copy of which was obtained by The New York Times.
The immediate next step for the agency is to “acknowledge the war has changed,” the document said.
The document’s tone reflects alarm among C.D.C. scientists about Delta’s spread across the U.S., said a federal official who has seen the research described in the document.
There were 71,000 new cases per day on average in the United States, as of Thursday. The new data suggest that vaccinated people are spreading the virus and contributing to those numbers — although probably to a far lesser degree than the unvaccinated.
Walensky has called transmission by vaccinated people a rare event, but other scientists have suggested it may be more common than once thought.
The C.D.C. recommended that vaccinated people wear masks indoors in public settings in communities with high transmission of the virus.
But the internal document hints that even that recommendation may not go far enough. “Given higher transmissibility and current vaccine coverage, universal masking is essential,” the document said.
Detailed analysis of the spread of cases showed that people infected with Delta carry enormous amounts of virus in their nose and throat, regardless of vaccination status, according to the C.D.C. document.
Infection with the Delta variant may be more likely to lead to severe illness, the document noted. Studies from Canada and Scotland found that people infected with the variant are more likely to be hospitalized, while research in Singapore indicated that they are more likely to require oxygen.
Still, the C.D.C.’s figures show that the vaccines are highly effective in preventing serious illness, hospitalization and death in vaccinated people, experts said.