If it's listed in the job requirements, then it's up to the applicant to prepare by getting vaccinated. If it's not listed as a requirement, then someone asking you to do it is not legally binding.
Whether it's not hiring because now they need to be vaccinated, or firing because they refuse to be vaccinated, I think this is all understandable in the face of a global pandemic. Situations change and we too, must adapt.
My mum was able to find a job many decades back with no knowledge of how to use Microsoft. With time, and as the company grew with it, of course staff need to be more proficient with IT and tech. They then offered upgrading skills/courses for current employees, and made this a requirement for their new hires. Supposing the employees didn't want to take the upgrading courses, can they really complain if they are then fired for not having the right skills to do their job? I should think no.
If it's listed in the job requirements, then it's up to the applicant to prepare by getting vaccinated. If it's not listed as a requirement, then someone asking you to do it is not legally binding.