I would not be in favor of denying health insurance claims but I would be less averse to allowing health insurance companies to factor in certain chronically risky behaviors when calculating health insurance premiums.

For example, a smoker who is not actively engaged in a smoking cessation program or someone who is morbidly obese by choice and not actively engaged in a medical weight loss program should be paying higher health-insurance premiums to offset their increased costs. (The former is not uncommon and while the latter may be controversial it is not necessarily a niche perspective. [1])

So yes, I think the same logic should apply to individuals who choose not to receive vaccines.

[1] https://pubmed.ncbi.nlm.nih.gov/19548556/