A research letter yesterday in JAMA Network Open ties large gatherings of unvaccinated students and nonstudents at US universities during last spring's National Collegiate Athletic Association (NCAA) March Madness basketball tournament to COVID-19 outbreaks in the surrounding community.Ashley L.
O'Donoghue, PhD, at Beth Israel Deaconess Medical Center in Boston, conducted a difference-in-differences analysis to compare COVID-19 infection rates in counties surrounding the 64 universities that competed in the mid-March 2021 NCAA Men's Division I Basketball Tournament with counties in the same states with universities that were not competing.At that time, new infections in counties with both competing and noncompeting universities were in