We Never Know
No Slack
There are few *guarantees* in life. No black and white available.
But there *is* reasonable risk assessment and mitigation.
Those that are allowed to get vaccines and that do not get them are a societal menace. Reasonable mitigation of that menace can and should be done. And that can involve refusal of services.
If John goes to a restaurant that has fully vaccinated 50 people eating in it and is refused service because he us unvaccinated, the risk is minimal being the vaccine is 96% effective.
Not to mention there could be 5 of the vaccinated people in there carrying the virus and could spread it to the other vaccinated people. .