https://techcrunch.com/2021/06/24/companies-navigate-ethical-minefield-to-build-proof-of-vaccination-apps/

In the U.S, after you get vaccinated against COVID-19 you are given a small paper card issued by the CDC that is essentially the only evidence that you’ve received your shots. It might seem like a flimsy level of proof, one that you could easily lose, but replacing that paper copy with a digital one has become a political lightning rod in America.

In spite of that, many companies are attempting to attack the problem to produce a viable form of digital proof, sometimes called vaccine passports. For all intents and purposes, what many call a vaccine passport is simply proof you’ve been vaccinated that you can carry on your smartphone, rather than on a card in your wallet.