Realistically that would mean vaccine passes so that you can only come into certain places if you can prove you have been vaccinated - and those can be made har

Realistically that would mean vaccine passes so that you can only come into certain places if you can prove you have been vaccinated - and those can be made hard to fake if we set up a digital certificate system. If each vaccine provider had a digital certificate signed by the relevant health authorities and then that was signed by a root US gov cert that everybody could download the public cert for, it would be virtually impossible to produce a fake one, and it would be pretty obvious which provider had faked the records. We could even burn the entire system once enough people have been vaccinated, by publishing the secret key of the root cert.