I have explained this may be 102 times on this forum...
as to what is the function of vaccine and how they work.
For the 103rd time, any vaccine in history does NOT build a protective dome around you. I wish it could, then voila no more infections if those vaccines could build a plastic dome around you.
I had my smallpox vaccine between age 5 and 6. I got sick with smallpox at age 8. So it did not prevent infection. But what the vaccine probably did for me was to prepare my body on how to fight the virus. May be that is why I did not join the group of 30% smallpox mortality group and still alive and healthy at age 81.
Function of covid vaccine is no different. If you are exposed to a load of virus from an infected person near you, you will inhale the virus into your respiratory system, even if vaccinated. And you can get sick EITHER symptomatic or Asymptomatic depending upon quantity of virus inhaled and how quickly your body can destroy the virus. But with vaccination your body will hopefully already have anti-bodies ready to fight the virus. Without those anti-bodies your body could mount a over-the-top response to that unfamiliar virus and that can damage your lungs permanently from your own white cells. In short, you have much better chance to avoid getting so seriously sick from covid to need ventilators isolated in a hospital.
So, when I am on a cruise ship, I would prefer only vaccinated passengers. Because they are less likely to get seriously sick on the ship and exude large loads of virus material. Vaccinated passengers could still test positive for covid, but with no symptoms or minor symptoms, they will not be exporting huge amounts of virus material in air in a closed ship.
Theoretically
So unvaccinated folks with mild or no symptoms but Covid positive will exude “large loads of virus material”?
And unvaxed folks who have had the virus already? You don’t want them on cruise ships with you?