Why don't they just cancel football until a vaccine is developed?

The precautions are more to limit the spread, not as much to protect the individual athletes. However they still don't know how or why it affects some differently than others. My wife's primary care doctor, who is also in our Sunday school class, told her he has had over 70 of his regular patients hospitalized to date because of COVID-19 complications and the worst case of all was an otherwise perfectly healthy 27 year old.

No chance in hell.

The 27 year old wasn't a pro athlete. No pro athletes have died from it. How are they going to spread it with no exposure to the fans or stadium employees other than refs.