There is talk of the NHS app being used for vaccination passports. If so, then people need to be aware that registering it is quite a palaver and if in weeks to come, there is a sudden rush in demand, it may be better to set up the login it requires sooner rather than later.
As well as your NHS number (we found ours were out of date and that was a problem in itself), you have to submit a passport or driving licence photo and then a scan of your face which goes off to be verified against the photo while you wait for this to be approved. For some reason, I had to do a video and some voice commands whereas Mrs R did not. Plus there are the usual email and phone text verification checks. You are talked through the whole process step by step but it does take a while and if any one step fails, it could take a while to resolve.