Erie County has already announced that to attend a Buffalo Bills or Sabres game in 2021-22 you will need to be vaccinated as both facilities are publicly owned. In New York you can have to vaccinated or have a negative test and in that state they already have a voluntary app that you can load you vax records to if you choose and it can be scanned at the gate. Those CDC cards people have been getting in the US could forged with no effort. In this country depending on where you get the shot the documentation can look very different so I would think something universal will need to be produced for those that want one.