Baseball season is here, and thousands of cheering fans are back in the ballparks after a year of empty seats and cardboard cutouts as fan stand-ins. Still cautious of the COVID-19 risk, most teams were keeping season openers to 20-30% capacity. Only the Texas Rangers planned a packed stadium for its home opener on April 5, a move President Joe Biden called irresponsible.

It isn’t just baseball – college basketball was allowing up to a quarter of seats filled for Final Four games, soccer season starts April 17, and promoters are planning professional fights in filled-to-capacity arenas.

Many of these attendance decisions are being made with minimal data about the heightened risk that players and fans face of getting COVID-19 at stadiums or arenas and spreading it the community.

There is one large-scale experiment that can offer some insight: the National Football League’s 2020 season.

Readd Fully at THE CONVERSATION</strong>