Major League Baseball, the N.B.A. and other sports leagues have started to let fans back into their stadiums and arenas with most teams limiting attendance to 10 or 20 percent of capacity, but some allowing more. The N.F.L. has even grander plans. Last week, Commissioner Roger Goodell said the league hoped to open all its stadiums at full capacity when the season kicks off in September.
“All of us in the N.F.L. want to see every one of our fans back,” Goodell said in a conference call with reporters.
Yet new research submitted to the scientific journal The Lancet in late March suggested that there was a link between the games that had large numbers of fans in the stands and an increase in the number of infections in locales near the stadiums.