The NFL and NFL Players Association have reached an agreement to set isolation time at five days for all players who test positive for COVID-19, matching new guidance announced Monday by the Centers for Disease Control, according to a memo obtained by ESPN.

The agreement includes both vaccinated and unvaccinated players and is contingent on the player being asymptomatic, or at least demonstrating that his symptoms are resolving, after the five-day period.

Speaking to reporters Tuesday night, NFL chief medical officer Dr. Allen Sills said the NFL's data during its recent surge supports the CDC's advice.

"The CDC's guidance is based on the fact that they don't feel that people are still at risk of spreading infection five days after their positive test," Sills said. "That mirrors what we've been seeing and why we are supportive and eager to implement this change."

Before Tuesday, the NFL had been requiring players to either test negative or meet a cycle threshold (CT) marker that would indicate they were no longer contagious. Sills said that testing has proved less valuable during the fast-moving omicron wave.

"We are always looking at all parts of the protocol and what our own data has told us," he said, "and we simply have not seen those players who have cleared and come back be associated with ongoing transmission. Certainly, in the pre-omicron era I should say. Obviously, with omicron it is relatively early to analyze that point but, I think the CDC has been very clear, they do not feel that people are infectious to others after the five days."

Under the former protocol, unvaccinated players were required to isolate for 10 days when they test positive. Vaccinated players may continue to "test out" of isolation sooner than five days, as soon as they test negative, either with two tests taken at the same time, or in combination with a cycle threshold (CT) test reading that indicates they are no longer contagious. Unvaccinated players will not be eligible to "test out" sooner than the five days.

Like the rest of the sports world and the country, the NFL has endured a massive COVID-19 surge over the past few weeks. The NFL and NFLPA have already altered their testing procedures, eliminating weekly testing for vaccinated players and focusing instead on those who have symptoms, but a record 106 players tested positive Monday.

Since Dec. 13, approximately 515 players have tested positive.