Which doesn’t address who is going to establish a standard for validity. Can it be ANY COVID vaccine? Or must it be a newer one - updated to provide protection against recent mutations? And how long is it good for? And does that vary by the particular immunization you received? And do these criteria vary by nation?
All questions that will have to be worked out before any of this can be implemented successfully. And then again we are actually going to have to get people immunized. Which isn’t going real well right now.
Just sayin’...