It isn’t yet mandatory across the NHS for covid vaccination in any units, whoever they treat (though local units may have their own guidelines, as often happens. These can be very inconsistent - for example, one of our haematology wards routinely swab their staff twice a week. However in ICU we don’t currently swab any staff routinely, even those looking after haematology patients).
It may well come, eventually. Some vaccinations are mandatory for particular roles (eg Hep B), others are not (eg Influenza).
Every OH department will have a policy that includes how to manage people who either decline a vaccine, are unable to have a vaccine or are non-responders to vaccine (this can happen with Hep B). There is usually an explicit vaccine refusal form where employees have to sign to say that they waive liability for workplace acquired infections and understand that there will be limits on the roles they are able to work in.
The main reason flu isn’t mandatory is because it varies from year to year and has widely variable effectiveness on response, how likely it is to prevent severe illness and how effective it is on transmission. This affects the ethics of mandating that staff have a vaccine.
High level evidence is still pending on covid vaccination and transmissibility in the real world (small studies so far from Israel), including the specific context of hospitals where the real test is how it reduces transmissibility over and above best infection control precautions (eg FFP3 mask + regular swab + daily lateral flow testing) - rather than with people going about their day to day business / social activities.
FWIW it’s also not clear what the best way of redeploying unvaccinated staff would be - immunosuppression comes in various forms and is not necessarily a marker of how likely someone is to develop severe covid.
In fact the drugs with high level evidence for treating severe covid are all high level immunosuppressants - dexamethasone, methylprednisolone, toculizumab. Cardiovascular comorbidities (diabetes, HTN) seem to be more involved in development of severe disease than anything else (probably due to over-expression of ACE receptor, which is what sars-Cov-2 uses to enter cells).
That doesn’t mean immunosuppressed people shouldn’t be concerned, and shouldn’t be protected. But if it becomes clear that vaccination has additional protection for patients over and above other infection control measures then the risk assessment of what to do with unvaccinated staff needs to include assessment of the relative risk in other areas as well as the potential impact on care of fewer available staff.
On a personal level, I’m incredibly pro-vaccine and have few issues with mandatory vaccinations for particular roles. But I’m sure you can appreciate that the potential implications of imposing this are quite complex and significant, and it is something that needs to be done on an operational / institutional level not by individual patients confronting individual staff members.