Yeah - not keen on vaccine passports. Apart from travel (which is presumably the requirement of the country you're going into) I can't think of any other vaccine that is mandatory for going about activities in the UK (recommended, yes, especially for certain jobs, but not required?). Some countries require the childhood vaccines for eg state education, but we don't here - so the fact other countries are doing it doesn't mean we automatically have to follow.
Obviously I have nothing against it, or any other vaccine, and I'm not entirely convinced by the "if we allow this, what will be next" argument. I accept this is currently a unique situation, so different measures may indeed be appropriate than have historically been used. But I'm just not keen on people being coerced into doing something they are otherwise reluctant to do, just to live life in their country of residence.