It would be most helpful for the entire crew to have the vaccine. A crew member has more contact with hundreds of passengers, making it more likely to be passed to passengers then fellow crew members in the short term.
I think Disney would not “require” the shot because of the currently unknown side effects. But Disney would offer the shot free (after signing a risk release form) for its crew. I also see Disney not immediately employing those who choose not to have the shot the first few months of sailing for SO many reasons.
Now as to the paying public. Ugh, not everyone wants the shot, religiously excepts science interference, believes in the science, or is healthy enough to get the shot. There’s talk about the vaccine working for 3 months, some longer, maybe a year. BUT... mutated strands of Covid have appear throughout this year just as the flu does every year. Both are constantly changing, requiring frequent tweaking of vaccines. But on the bright side there seem to be positive results coming from treatment of the virus recently. Those might even, let’s hope at some point, be available on the ship.
Will the risk be low enough to offer a mask free cruise? Maybe not for senior citizens or the immune compromised. Maybe theaters can be full again, but with masks. That really wouldn’t bother me because the person behind me in New York while I watched the Donna Summer musical had dragon breath!
So sadly, sailing with a Covid-19 free bubble cannot ever happen. But they are going to reduce problems to manageable lower levels hopefully soon. I’m hearing about an announcement from my daughters school coming out in mid November. So I remain positive science has a good chance of taking care of this. My daughter is pre-PA, working in research, and she’s been hearing things.
I intentionally did not address ports here. Just my Disney ship views.