This will never happen. Medical institution will never pass vaccinated data to a third party. To be able to gather such data, you must operate on a government level. You need to have connection to governments and ministry of health of all countries. Can you even imagine what kind of security you must have, to prevent data leak? Or what consequences you will face if you got hacked. You 5 page whitepaper dont have a single sentence of your security level.

Or your idea is that a vaccinated person must visit your webpage and make a registration, that he is vaccinated? You will spend million on promotion program just to show to every person in the world that such webpage exist.