CDC Publishes Scientific Paper Jointly Authored with the NFL on COVID-19 Lessons from the 2020 Season Applicable Beyond Football

Data from NFL's daily testing and contact tracing programs created a new definition of High-Risk Contacts

High-Risk Contacts definition and NFL's Intensive Protocol reduced spread of the virus and provide valuable insight for containing spread in society

NEW YORK (January 25, 2021) – The Centers for Disease Control and Prevention (CDC) today published a paper jointly authored by CDC and NFL-NFLPA medical experts and epidemiologists. The publication shares the benefit of the NFL's COVID-19 mitigation strategy, with elements that the CDC paper says can be broadly applicable throughout society to limit the spread of the virus, including "to settings such as long-term care facilities, schools, and high-density environments."

The NFL, through its season-long, robust testing and contact tracing programs, found that transmission of the virus occurred in less than 15 minutes of cumulative interaction between individuals, the timeframe initially used in the CDC's definition of "close contact." Evidence generated by the NFL data led to a revised definition of High-Risk Contacts that led contact tracers and medical experts to consider information beyond duration and distance, such as masking and ventilation. The NFL data also led to a mid-season launch of the NFL's Intensive Protocol, a stricter set of virus prevention measures imposed at an NFL club in response to a positive case and eventually adopted by all clubs.

The new High-Risk Contact definition, used in the NFL and derived from the NFL's findings, includes "assessment of face mask use (e.g., medical mask versus cloth face covering, proper mask use for both infected person and contact, and any mask removal to eat or drink) and setting and ventilation (e.g., outdoor, indoor large volume, indoor small volume and during transportation)." These criteria were used to effectively identify and quarantine any person who had been exposed to an infected individual in an effort to mitigate the spread of the virus.

Together with continuous evidence review throughout the season, the new definition of High-Risk Contact and implementation of the NFL's Intensive Protocol decreased High-Risk Contacts, continuously improved mitigation measures, and prevented spread of the virus within the NFL environment. These lessons from the NFL season are applicable to non-sports settings, such as essential workplaces, long-term care facilities, and schools, the publication said.

"We are grateful for the CDC's ongoing guidance and collaboration since the beginning of this COVID-19 pandemic," said Dr. Allen Sills, the NFL's Chief Medical Officer and a co-author of the paper. "The publication today is a demonstration of the league's commitment to meaningfully contribute to the body of medical and scientific knowledge about the virus. Partnering with the CDC to share findings from our season with the public health community is important to society as other workplaces, institutions and organizations look for effective strategies to reduce the risk of the virus."

The publication cites 20 individuals from October 15 – November 21 who were identified as High-Risk Contacts and later became positive cases. To-date, that figure has increased from 20 to 37 individuals. The High-Risk Contact definition and accompanying protocols enabled identification and proactive quarantine of those 37 individuals in the early days of their infections.

The Intensive Protocol, which has evolved throughout the NFL season based on ongoing analysis of testing and contact tracing data, was deemed in the publication "an effective mitigation measure." No High-Risk Contacts were identified in 71% of cases where the infected individual's club was under those stricter measures. Further, the Intensive Protocol decreased close contacts by 60% from October 1 – November 21, when 29 of 32 clubs spent 431 days under the Intensive Protocol.

The NFL's Intensive Protocol includes virtual-only meetings; limited outdoor gatherings; increased physical distancing; mask wearing at all times, including for players during practice; and eliminating group meals. The league began implementing the Intensive Protocol on October 1, 2020, for any club with a COVID-19 positive case and the recent opposing team if exposed during a game. Beginning November 21, 2020, a league-wide adoption of the Intensive Protocol was mandated though the end of the season in recognition of its benefits in preventing COVID-19 spread.

PHS - Intensive Protocol Graphic

The research paper, titled "Implementation and Evolution of Mitigation Measures, Testing, and Contact Tracing in the National Football League, August 9–November 21, 2020," was published in in the CDC's Morbidity and Mortality Weekly Report (MMWR), which the agency calls its "primary vehicle for scientific publication of timely, reliable, authoritative, accurate, objective, and useful public health information and recommendations."

The publication concludes: "In the NFL, COVID-19 transmission was identified in persons with <15 minutes of consecutive or cumulative interaction and was reduced through implementation of an intensive protocol focused on environmental change, increased personal protection, avoidance of high-risk interactions such as vehicle sharing, eating in the same room or common areas, and expansion of the components of contact tracing to incorporate high-risk contact designations. Although the protocols implemented by the NFL were resource-intensive, strategies such as accounting for the specific characteristics of the close contact, in addition to time and duration, and creation of an intensive protocol are applicable to other settings, including essential workplaces, long-term care facilities, and schools."

The paper published today in the CDC's MMWR is in the public domain and available here.

For additional information about the NFL's COVID-19 protocols, please visit


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Megan Grant