I want to dispel some of the math in regards to the efficacy rate. People hear 95% efficacy, and think that means 5% of any particular group of people will get the virus, even with a vaccine. This is NOT the case.
They think if 1,000 vaccinated people are on board the ship, 50 people could contract the virus. Again, this is NOT the case.
During the Pfizer trials, there were approximately 21K people in both the trial and the control groups. In the vaccinated group, of the 21K people, 8 people contracted the virus. Clearly 8 is not 5% of 21,000 people.
What it means is that whatever a person's chance is, of contracting the virus....it is reduced by 95%. The control groups, whether Pfizer or Moderna, places the contraction rate at somewhere around 1%, Pfizer a little lower, Moderna a little higher, but 1% is a good average. Now...the argument could be made that it may be a little higher than 1%. In certain pockets of people, it might be higher. So...the point is that if the chance, without a vaccine, is 1%, it reduces the chance of getting it by 95% (of that 1%)
So, if Pfizer's control group rate is 0.77%, 5% of that is 0.000385%. If you take that number times the 21K in the trial group, it comes out to....8 people.
Now, like I said, the argument could be made that 1% is a little low. And, the argument could definitely be made that in a cruise ship setting, the chances of unvaccinated people spreading the virus is higher, maybe even much higher than 1%. That said, studies are showing, though not proven yet, that not only does the vaccine reduce one's chance of contracting the vaccine, it also highly reduces the transmissibility of it, even if someone DOES get the virus. So, if someone does get the virus, on a fully vaccinated (or at least adults) ship ...the chances are small that they will actually pass it on, and it shouldn't lead to some catastrophic outbreak.