Some of those who have chosen not to get vaccinated are those already recovered from Covid, who now have natural immunity. This includes many essential workers and first responders, who worked throughout 2020 without the protection of a vaccine.

That leaves the subset of non-immune people who are unvaccinated. If this hypothetical person is reckless (as your comment suggests), should they not have already been infected in the past 18 months? If they were not infected in 18 months, that suggests at least some ability to isolate and self-monitor.