The Centers for Disease Control and Prevention recommended Tuesday that vaccinated Americans wear masks indoors in certain circumstances — the latest step in the nation’s escalating fight against the highly transmissible delta variant of the coronavirus.
The agency advised that vaccinated people who live in high-transmission places wear masks in indoor public spaces, according to three people familiar with the guidance. It also recommended that vaccinated people with vulnerable household members, including young children and those who are immunocompromised, wear masks indoors in public spaces.
The agency also called for universal masking for all teachers, staff members and students in schools, regardless of their vaccination status.
CDC Director Rochelle Walensky said the changes were spurred by “worrisome” new data showing that vaccinated and unvaccinated people infected by the delta variant carry viral loads that “are actually quite similar." That suggests that some vaccinated people “may be contagious and spread the virus to others" even though they are unlikely to become severely ill because of the vaccines’ protection. Such transmission did not happen in any significant way with earlier strains.
Albert Ko, an epidemiologist at the Yale School of Public Health, said in an email ahead of the CDC announcement that if vaccinated and unvaccinated people carry similar viral loads, new restrictions were necessary. “There are several hoops in logic to pin down (duration of viral shedding being one), but the finding if rigorously proven would be concerning,” Ko said.
But in June the delta began to spread at exponential rates, and Helix scientist William Lee said Tuesday he estimates it accounts for more than 90 percent of infections nationally. The alpha, by contrast, is seen in only about 3 percent of positive tests. “It’s almost gone,” Lee said.
News of the CDC’s changed guidance was welcomed by medical and public health experts many of whom had sought greater restrictions. People infected with the delta variant appear to carry a viral load that is 1,000 times higher than earlier versions of the virus, they said, and can easily spread it.
“Nobody wants to go backward, but you have to deal with the facts on the ground, and the facts on the ground are that it’s a pretty scary time, and there are a lot of vulnerable people,” said Robert Wachter, chairman of the department of medicine at the University of California at San Francisco. “I think the biggest thing we got wrong was not anticipating that thirty percent of the country would choose not to be vaccinated.”
Luis Schang, a Cornell University virologist, applauded the changes and said wearing a mask represents a “small effort” given the suffering caused by the pandemic.
“It’s not a permanent thing. That’s an important thing to highlight,” Schang said. He said the vaccines are still working very well and vaccination rates continue to rise. “This is not something we have to do for years. This is weeks, perhaps a couple of months.”
Natalie Dean, a biostatistician at Emory University, noted that the picture in the United States has changed significantly in recent weeks.
“Things were going all right for a little bit. … Now it’s like, well, what are we doing here? The trends are not good,” she said, adding: “The situation has evolved. Literally.”
In mid-July, for instance, when Los Angeles County became the first major county to reimpose masking requirements indoors, it faced angry denunciations from the elected officials of a half-dozen local towns that are part of the county.
“They waited too long,” said one Biden official who spoke on the condition of anonymity to discuss confidential conversations.
“People don’t realize how bad delta is,” James Lawler, an infectious-disease doctor at the University of Nebraska, said in an email. “We are looking at transmission dynamics at least as bad as in the fall — with no mitigation measures in place in most states with low [vaccination] rates.”
Some of the CDC’s international partners had already moved to reinstate mask mandates or delay plans to loosen them. In Israel, an indoor mask mandate was lifted on June 15, only to be reinstated on June 25 as cases of delta surged. Other nations, including Australia and France, have seen regional rules on mask-wearing return this summer amid new outbreaks caused by the delta variant.
"Everyone is entitled to their own opinion, but not their own facts." - Daniel Patrick Moynihan