A COVID19 Vaccination Passport program sounds impressive but worthless. All that a person needs is a vaccination card, Hey!, something that already exists.
Ah I forgot to say a person can laminate the card to better preserve it.
True. I still have my old school shot / vaccination record and I actually ended up w two more shot / vaccination records from my time in the Army. I think I have been vaccinated against everything known to science, that is until now. I am happy with the card. All that documentation and $1.50 might get me a cup of coffee. Data bases with unimaginable amounts of information on people are all over the place, not just in governments, things are at a point where the right hand can not communicate w the left. The simple little card will do just fine for the intended purposes everybody keeps talking about.
They type of proof is highly dependent on the value and risk that having that proof provides and the amount of trust between the person presenting it and the entity accepting it.
To show your doctor your vaccinations so that you're getting the best healthcare you can, there's a high trust because you want good care, the document doesn't need to provide that trust for you.
To have a friend over for dinner that tells you they're vaccinated, you don't even need the card. You'll simply trust them without showing any proof at all.
To give a random person the value of eliminating all mitigation items to create a bubble like environment, there's a trust factor needed. Whatever is used for the verification process is providing that trust. The vaccination card people have today isn't suitable for providing that trust. Doesn't have to be a smart app, but whatever it is, it's not just the thing in your hand. It's the entire system that thing represents that's providing the trust factor to allow an entity to believe that a random person they have not knowledge of should be allowed into the bubble.
Something that's just a key and looks up in a back end database, assuming the data is valid, has a high trust factor. Without the database, something that's difficult to fake can provide the trust factor.
Just look at a WDW park ticket. It's not just some ticket that grants you access. There's an entire system behind it designed to validate that it's a real ticket, issued to a specific person, and not used by anyone else. And, that's just to get into the magic bubble.