CDC, NFL hope findings of what makes a close contact high risk will limit public spread of COVID-19

A paper published Monday by the Centers for Disease Control and Prevention stated that during the season, the NFL found that transmission of the virus that causes COVID-19 occurred in less than 15 minutes of cumulative contact between individuals -- the timeframe the CDC initially used in its definition of close contact. That led the NFL to redefine what made a close contact high risk -- factors like masking and ventilation -- findings that the CDC and the NFL hope will be broadly applicable to the public to limit the spread of the virus, especially in schools, long-term care facilities and high-density essential workplaces, like manufacturing centers.

The paper, jointly written by the CDC and the NFL and NFL Players Association's medical experts and epidemiologists, relied on the reams of data generated from the NFL's season-long daily testing and contact tracing program. The NFL is a unique case because of the vast resources it had at its disposal to test players, coaches and staff every day, to quickly deploy contact tracers when there were positive cases, and to use genomic sequencing to determine how the virus was spreading within teams.

But from the start of the season, the NFL said it wanted to share what it learned with public health agencies in the hopes that what they learned could help others navigate the pandemic.  What was gleaned from the season and how the protocols evolved -- particularly the creation of the intensive protocol, which stopped in-person meetings -- suggest recommendations that could be useful in other settings.

"It's important to recognize that the most impactful intervention was not testing or tracking devices," said Dr. Allen Sills, the NFL's chief medical officer. "The most impactful interventions were universal use of facemasks, holding meetings outside and minimizing in-person meetings, closing dining rooms -- those all have broad applicability outside of football."

Also important were the quality of the masks being used, and air flow and ventilation. That is why in-person meetings were eventually forbidden in the NFL, even if people were able to be 6 feet away in a room, and why all meals at team facilities had to be grab and go -- eating together was an area of vulnerability.

And the paper showed the importance of isolating and quarantining people who were deemed high-risk close contacts of an infected person. That mid-season adjustment in the NFL protocol was designed to limit the spread of the virus. To date, 37 individuals who were isolated after being a high-risk close contact later tested positive.

The intensive protocol -- which included virtual meetings, mask-wearing at all times, including during practice, and elimination of group meals -- was put in place at the start of October for any team that had a positive case. In mid-November, the league mandated that all teams operate in the intensive protocol. According to the paper, no high-risk contacts were identified in 71% of cases where the club was in the intensive protocol. The paper called it "an effective mitigation measure."

Sills said on a conference call that the NFL found no evidence of virus transmission during games -- daily testing meant very few infected players were on the field at all, and players spent very little time in close contact during a game -- and also had traced no outbreaks or clusters to games that allowed fans.