The NFL's chief medical officer, Dr. Allen Sills, said Thursday that the league's amended COVID-19 protocols were based on findings that show asymptomatic people are not spreading the virus.

Speaking in an interview with NFL Network, Sills said the league had reason to believe that it is wise to halt weekly testing of vaccinated players and instead target those who voluntarily report symptoms.

"We've really not seen this phenomenon that people have discussed, which is asymptomatic people in the facility spreading the virus to others," Sills said. "As we've gone back and looked throughout the entire season, what we've seen consistently is that when people have symptoms, that's when they seem to be contagious to others. And that's why we're asking people to come forward and acknowledge symptoms because that's the point at which they're vulnerable and the point at which they expose themselves to others."

Sills went on to say the data's findings held "particularly true" with regards to the Omicron variant.

The doctor's statements stand in contrast to previously believed information about the pandemic, namely that people can still spread COVID-19 if they are carrying the virus but not displaying its symptoms.

When the NFL first began seeing a sharp rise in cases last week, Sills told reporters that roughly two-thirds of more than 100 COVID-positive players were asymptomatic.