What does the CDC and the cruise lines propose to do with folks that have already had Covid and not have been vaccinated?
For Carnival they have to request an exemption and try to be part of the 5% unvaccinated ...The CDC doesnt regard them as immune...
If they can prove they were diagnosed and hospitalized with Covid and can prove it, they maybe OK, otherwise they would be treated as unvaccinated deplorables. - Tom
Keep in mind the boarding process on a cruise ship involves processing documents of thousands of passengers in 4-5 hours.
A vaccine document examination will only take a minute or 2.
To examine hospital & medical records of recovery from covid will require much longer time. That is what makes it impractical for more than 5% of passengers.
Not let them on would be my guess.