NFL COVID-19 tracking yields lessons for fine-tuning control measuresAn intensive COVID-19 prevention and surveillance system that the National Football League (NFL) put in place this season identified certain types of risky in-club transmission, which helped officials revise its high-risk contact definition and improve its protocols.Representatives from the NFL and their colleagues, including Michael Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy, publisher of CIDRAP News, detailed their findings today in Morbidity and Mortality Weekly Report (MMWR).As part of the NFL's COVID-19 measures established last July, players and staff wore masks, physically distanced, were frequently tested, and wore