the thing about "vaccine passports" for covid-19 is that the vaccines aren't going to work very well against the increasingly complicated variants. it's not even a philosophical debate about whether it's acceptable or not; the reality is that the science doesn't support it as rational.

and, as i've pointed out, and many others have pointed out, a vaccine will never work as well as natural immunity.

but, there's an underlying error that people have to adjust to - people are trying to compare covid to something like polio, which has a low mutation rate and doesn't require multiple vaccinations. you're going to need to get vaccinated for covid-19 every year, and potentially even more frequently than that.

so, the proper comparison is not to polio, but to the flu.

and, i know of no countries that require travelers to get flu shots before entering, at this time.

it's the kind of idea that comes up when you get a bunch of arts students trying to discuss science; it's not grounded in evidence, and while that doesn't mean it won't happen, it will be a sad day, indeed, if it does.