Reversing a decision made just two months ago, the Centers for Disease Control and Prevention is expected to recommend Tuesday that people vaccinated against the coronavirus return to wearing masks indoors in certain areas of the country.
The change follows reports of increases in breakthrough infections with the Delta variant of the virus in fully vaccinated individuals, as well as increases in cases in regions with low vaccination rates. However, the new policy would mean a sharp turn from the agency’s position since May that vaccinated people will not have to wear masks in most indoor spaces.
As recently as last week, an agency spokesman said the CDC had no plans to change its guidelines unless there was a major change in science. Federal officials met on Sunday evening to review new evidence that may have led to the reversal, CNN reported Tuesday.
“I think that’s great,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center in New York. Based on what scientists are learning about the Delta variant’s ability to cause breakthrough infections, she said, “This is a step in the right direction.”
The CDC’s first guidance in May said people fully protected from the coronavirus could stay mask-free indoors, but recommended that unvaccinated people continue to wear masks. These recommendations were harshly criticized by some experts who said it was premature given the large numbers of unvaccinated people in the country.
Dr. Rochelle Walensky, the director of the CDC, pointed to two scientific findings as essential factors at the time. Few vaccinated people become infected with the virus, and transmission seems to be even rarer, she noted; and the vaccines appear to be effective against all known variants of the coronavirus.
A day after the announcement, the agency released results from a large study showing that 94 percent of those who received two doses and 82 percent of those who received two doses of mRNA vaccines manufactured by Pfizer-BioNTech and Moderna were effective in preventing symptomatic disease that they had received were effective at one dose.
But that data and the CDC’s decision were based on infections from previous versions of the virus before the Delta variant crossed the country. Reports of clusters of infection in fully immunized individuals suggest that the variant may break the vaccine barrier more often than previous iterations of the virus.