Hamlin suffered cardiac arrest during the game last year and was rushed to the hospital. Many people supposed that the covid vaccine caused his heart attack. That's a fair assumption because so many young athletes are collapsing and dying. The medical establishment now admits that the vaccine can cause myocarditis.
However, search the Internet and you won't learn whether Hamlin had the vaccine or not. You won't learn whether the Buffalo Bills mandated the vaccine for its players. The team did require all fans at its stadium to show proof of vaccination, so you decided about the players. You won't discover whether the NFL mandated it, either, although there's this curious headline in the Washington Post: "The NFL requires coronavirus vaccines without mandating coronavirus vaccines." Apparently the league didn't establish a mandate, but it did decide to punish any team whose sick players interrupted play. Something to do with the players' union.
We still don't know about Hamlin's vaccination. Wonder why that is.