While I can't comment on any vaccine link, it's not unusual for athletes to die in their prime, especially American football players. It's been happening for many years, especially since the late 70s as the armor (uniforms) got "better" and thus encouraged even harder hits, especially to the head. That sport is so amazingly violent; they get hit so hard, it really traumatizes the brain. A few years ago there was a big social movement against the sport as all the evidence of brain injuries that the league has been suppressing came to light, but that movement seems to have fizzled out and we are back to just accepting it when young people die from the game.