The Centers for Disease Control and Prevention is expected to recommend that fully vaccinated people start wearing masks indoors again as the COVID-19 Delta variant continues to spread across the country. According to CNN, the government agency will hold a briefing about the matter today (July 27) at 3 p.m. EST.

The news marks a policy reversal from the CDC, which said in May that fully vaccinated people didn’t need to wear masks in most settings anymore, both indoors and outside.

“The Delta variant is spreading with incredible efficiency. It is much more aggressive and transmissible than previously circulating COVID-19 strains causing more than 83 [percent] of recent cases,” CDC Director Dr. Rochelle Walensky tweeted on Monday (July 26). “Vaccination is our way out of this pandemic.”

During the briefing, the CDC is also expected to recommend that everyone in K-12 schools wear a mask, regardless of their vaccination status. According to CNBC, federal health officials are concerned that the highly contagious Delta variant will cause another infection surge in the U.S. this fall, when students and adults are expected to return to their traditional school and work settings.

Health officials also fear that the Delta variant is taking a large toll on states with low vaccination rates. Those states will soon be forced to reintroduce mask mandates to stop the spread of the disease.

On Sunday (July 25), White House Chief Medical Advisor Dr. Anthony Fauci confirmed the reintroduction of masks was “under active consideration” by the CDC.

“It’s a dynamic situation. It’s a work in progress, it evolves like in so many other areas of the pandemic,” he told CNN. “You’ve got to look at the data.”

While fully vaccinated people still represent a small number of individuals carrying the disease, some vaccinated people could be carrying higher levels of the virus than was previously known, CNBC writes. Dr. Walensky will announce the CDC’s decision later today. See her tweet below.