Here's how the NFL tackled the spread of COVID-19 among players, staff

Beyond proximity, NFL data indicate there are other important factors around COVID-19 transmission such as whether or not individuals wear a mask, the type of mask as well as ventilation and airflow. (NFL)

Despite a global pandemic, one of the nation's top sports leagues got all 256 regular-season games played within 17 weeks in 2020.

And one of the first key lessons that helped the NFL drive forward? Officials learned playing football itself did not spread COVID-19.

"There is no evidence that the virus crossed the line of scrimmage, so to speak," said Allen Sills, M.D., the NFL's chief medical officer, during a call with reporters Monday.

Despite the close physical contact during a football game, genomic epidemiology data analyzed by the NFL indicate there was no on-field transmission of the virus during the league's games, Christina Mack, M.D., an IQVIA epidemiologist and adviser to the NFL, said during the press call.

"If you look at the data, one thing that shines through is that context matters. Football is played in a well-ventilated area, with a lot of airflow, and with brief interactions on the field," she said.

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What were some of the other ways the league tackled the spread of COVID-19?

In a new scientific paper jointly published with the NFL, the Centers for Disease Control and Prevention (CDC) credited the league for implementing an intensive protocol for players and staff that served as "an effective mitigation measure." From early August to early November, of 623,000 RT-PCR tests performed on about 11,400 NFL players and staff members, only 329 (approximately 2.9%) laboratory-confirmed cases of COVID-19 were identified, according to NFL officials.

According to the CDC report, the NFL's COVID-19 mitigation strategy 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."

"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," said Sills, who, along with Mack, co-authored the CDC study.

Lessons from the NFL's strategy

The NFL and the NFL Players Association (NFLPA) began the 2020 football season in July, implementing extensive mitigation and surveillance measures in facilities and during travel and gameplay. Protocols included mandatory masking, physical distancing, frequent hand-washing, facility disinfection, restricted facility access and regular, frequent testing of players and staff members.

The NFL consists of 32 member clubs based in 24 states.

Comparing the NFL's COVID-19 strategy to the football fundamentals of blocking and tackling, Sills said the league relied on basic mitigation measures: universal use of masks, limited indoor and in-person meetings, prompt reporting of symptoms and isolating symptomatic individuals.

As part of contact tracing efforts, the league required players and staff to use wearable devices provided by Kinexon that can warn users if they are too close to one another as well as record proximity and duration of interactions among users to trace and evaluate chains of infection.

The biggest insight from all those data collected? All close contacts are not created equal, Sills said.

"Some contacts convey higher risk, and circumstances matter," he said.

By midseason in late September and early October, the NFL's contact tracing efforts found that transmission of the virus occurred in less than 15 minutes of cumulative interaction between individuals. And those interactions were taking place off the playing field.

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While proximity to someone who has the virus and the duration of the interaction matter, the NFL data indicated there are other important factors around transmission. "Whether or not individuals wear a mask and the type of mask, medical-grade versus cloth-based covering are also important as much as ventilation and airflow," Mack said.

That led the NFL to adjust its strategy and revise its definition of "high-risk contacts" that considered factors such as mask use, indoor versus outdoor setting and room ventilation in addition to proximity and duration of interaction.

The NFL also developed an intensive protocol that imposed a stricter set of virus prevention measures imposed at an NFL club in response to a positive case. According to the NFL’s most recent data, approximately 881,510 tests were administered to players and personnel between Aug. 1 and Dec. 26, and 222 players and 396 other personnel tested positive during that time period.

The protocol, which was adopted leaguewide in November, effectively prevented the occurrence of high-risk interactions, with no high-risk contacts identified for 71% of traced cases at clubs under the intensive protocol, according to the study.

The NFL's new "high-risk contact" definition and accompanying protocols enabled identification and proactive quarantine of 37 individuals in the early days of their infections.

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Applying the lessons that the NFL learned, workplaces and schools should consider shifting to virtual-only meetings, closing break rooms or other common areas, increasing physical distancing and requiring mask-wearing at all times, Mack said.

Other high-risk interactions should be avoided, including riding together in cars and eating in the same room or common areas, the study said.

For the NFL, the most impactful interventions were not resource-intensive, Sills said.

"The most impactful interventions can be applied anywhere, including universal use of face masks, moving meetings outside or closing dining rooms, and strict quarantines. That has broad applicability beyond football to include schools and nursing homes," he said.