With flu probably about 50% of passengers have been vaccinated. Another 30% or so may already have some level of immunity. With covid nobody (or relatively few

With flu probably about 50% of passengers have been vaccinated. Another 30% or so may already have some level of immunity. With covid nobody (or relatively few people who have had it by now) has immunity and there is no vaccine. We do have numerous examples of noroviruses infecting a lot of people on cruise ships.