There is no free market. Due to the Affordable Care Act (Obamacare), medical insurers aren't legally allowed to set premiums based on vaccination status.

https://www.healthcare.gov/how-plans-set-your-premiums/

Let's not pretend that insurance based payment even remotely resembled a free market before.

Medical services do not have price-elastic demand just because they are offered in a free market. It's the other way actually; I'd imagine medical services are some of the most price-inelastic things you can buy.