How do you know? Nobody would want them in their little hospitals. Are people going to have to prove they had flu shots? It can be as bad or worse than covid.
Masks are proven useless and as long as those worried are vaccinated it should be of no concern to anyone if others are not.
This whole thing is silly and tyrannical.
Local health facility relationships are a requirement of the CDC guidelines/certificate. Wouldn't matter, the lines have had those relationships anyway. And ships don't have inpatient care, so an ill passenger will be disembarked and sent to local providers. Who are happy to have them. Maybe many of these regulations are silly, but that doesn't matter to the business' who have to comply with them. Which is the issue. It's a classic case of governmental regulation, particularly when you consider the interest of the US in most cruises is a half day at the beginning, another at the end, of a 4 to very long international voyage. The companies have little choice but comply.