Meh, still a red herring.
But I've had to show vaccination records 4 months ago when I enrolled my son at the junior high. I had to do the same with my daughters - and before that when they started elementary school. While not a vaccine, I just had to provide my employer with proof a negative TB test. Medical staff often have to provide proof they've gotten the flu shot.
But if you want to do the history of time, there were vaccine passports for smallpox. So it has existed.
Now if we're talking on a personal level, I've never been asked had to prove it to a friend. But I doubt you have either. I did have a friend confirm my family had either had chicken pox/vaccine when she was diagnosed with shingles 3 weeks ago, in an effort to protect us. But I don't actually think friends are asking each other to prove anything. In fact, I find most people, on both sides, are willingly volunteering that information.
But people need to stop acting like vaccination proof is new and acknowledge that this is public health crisis. Eventually this will go the way of flu shots and people won't be discussing it anymore.