Along_the_Wire it’s not even to do with wanting the vaccine or not, it’s about the principal of potentially permanently enforcing certain things to be off limits for those who haven’t had it, even when them needing it is unnecessary. Then the additional issue of it being formalised in a system which has the possibility of being expanded in to additional undesirable avenues and unfairly and expediently controlling the population with.
You could well be right that international travel might force some people’s arm when it comes to the vaccine, certainly in the near future while the virus isn’t perceived to be more subdued. However, governments already are and will be in conversations with each other about the extent to which they consider such things will be necessary or not going forwards and whether they will need to be in perpetuity. Airlines will also be part of the discussion.
It might end up being permanently aligned with, or in addition to, say current travel visa requirements - perhaps people from certain, say developed, countries might be allowed to fly to others without need for one (have a so-called “safe travel corridor” enforfed) , but other countries might be closed off.
The goalposts of which people could fly where and when might be more easily to move and restrict in future once such a system has been established, whether for political reasons in disputes with other countries, to restrict the ability of certain or all people to leave their country, or generally to reduce the level of global travel.