Originally Posted by merlin90

I don't know which states are doing what, exactly, but each state can, if it wishes, set up its own digital vaccine verification system. In California, for instance, I was able to submit the dates of both my doses along with my name to the system that the state established, and because that information matched against whichever database stores this information, I was sent a QR code and summary of my doses/dates that I can use to verify that I am vaccinated. I've not had to use this for anything yet and I honestly haven't heard of anyone else who has (some friends had to show their CDC card one time to get into Dodger Stadium) but I imagine other states have done something similar. It's not mandatory; more of a way to prove your vaccination status, if necessary, without worrying about losing your CDC card.