One issue is that the vaccines are not 100% effective. It would not be possible to know with certainty that particular person would not have gotten sick if they’d gotten the vaccine. I realize that wouldn’t necessarily rule out the idea but reduces the force of the equitable argument somewhat (at least to my mind)No vaccine is 100% effective. It's the rare one that is >90%. The annual flu vaccines are much less than 90% effective. On the good years, it's 40 or 50% effective. Yet, hospitals can require all employees to get the annual flu shot, with the usual exceptions for people with known allergies or medically valid reasons for avoiding those vaccines. That's not the same as refusing to pay for hospitalization costs if a vaccine refuser got seriously ill with Covid-19, but it does have legal teeth.\nAlso, some people get COVID and recover without requiring medical treatment, thereby developing immunity without the cost of a vaccine. I’d imagine that at least some of them would argue that they shouldn’t be required to cover the cost of vaccines for others.Most children who got measles recovered without medical treatment. But enough died that, once a measles vaccine was available, it became required for attending public schools (with the usual allowable exceptions). Same for polio.\n\nVaccines are cheap and highly effective preventative medicine. Hospitalization is very expensive.