I'm not so certain that'd be legal. The idea maybe would have a footing if wanting to prevent those who are actually infectious, e.g. requiring proof of a negat

I'm not so certain that'd be legal. The idea maybe would have a footing if wanting to prevent those who are actually infectious, e.g. requiring proof of a negative COVID test, and because these vaccines don't prevent infection - and may actually lead to it being easier to catch [and therefore spread] COVID - it isn't akin to a negative COVID test result.