Pixie "I think realistically, it will have to be each to their own risk, in the end. A passport won't help, if it can't differentiate between "can't" and "don't want to"."
of course it can. It will be perfectly simple for a "medical exemption" tag to be added to any IT system.
As I said earlier, I don't have an answer myself and thank goodness I don't need to have one. While I am firmly against compulsory vaccination, so far as a passport (international travel) goes, it won't be up to England what other countries do and any PASSPORT solution applied here will need to work in with the global system. The principle of required vaccinations for entry to certain countries is already well established.
So far as certification just for England or the UK, I foresee that there still will be a need for a contact tracing system, also there is the issue of unvaccinated people becoming a host group for virus variations which endanger us all.
and also as I have said, I don't think my ambivalent attitude would last more than milliseconds if my late Mum was still here and needed home or residential care.
There is also the 'who pays" issue. Any reasonably secure system will come with a cost. if its just the card given when you get the jab, or similar, you might as well not bother at all...too copyable, too shareable.