I think this is a valid point. They may need to add to the list people who can prove they either tested positive or have antibodies. I know my wife had to get vaccine titers to work in day care centers that prove her MMR shot is still active and working.
I don’t think we can look at past pandemics as evidence of what will happen this time. We have never had WDW shut down and then re-opened with many restrictions due to a pandemic. I don’t think it’s likely they will require proof of a vaccine if they can help it, but if the vaccine doesn’t lead to herd immunity or if it takes a long time (6+ months) they may consider it if enough people are vaccinated that they will have enough customers. I know your comment was just sarcasm, but they couldn’t open today to only people who were infected because there aren’t enough people to make that worth doing. If we get to over half the population vaccinated but case numbers still aren’t low enough to remove Covid restrictions (masks, distancing and capacity limits) it may be worth it to implement a plan to require vaccinations to get rid of that stuff and bring back larger crowds.
My opinion (no supporting evidence, just an opinion) is that mandatory vaccinations will not be required. The vast majority of people get vaccinated and are not part of the anti-vaxxer crowd. Right now, while the benefit side of the vaccine equation is know the risk side is not. Until it is, a rational person will hesitate to take it. It does not help that this is the first mRNA vaccine, so nobody can even compare it to other vaccines. If it in fact does not cause serious adverse reactions then I doubt that people will object.
At least covid does not have a 30% infection death rate like smallpox. The side effects of that vaccine were considered to be worth it compared to what happened if you got the disease.
If the vaccine does not lead to herd immunity, we are all going to have to learn to live with the disease. I say that because the implication for that to happen is that immunity would have to wane quickly after either the vaccination or the disease. So far, there is very little evidence that this will happen.
Another opinion - I think that the primary issue for WDW is overcoming everyone's fear of the disease. I am on the west coast of Florida, and we have not had any meaningful restrictions since the end of September. Regardless, people simply are not getting out and doing anything where a crowd is involved. Sure, there are always a few asshats out there, and they are always the ones who make the news, but when you go to a restaurant they are always less than half full, even on a weekend. They only exceptions are the outdoor areas. I have been to Magic Kingdom and Animal Kingdom post covid, and I didn't think it was crowded at all. Long lines - sure, but they moved fast. But perception is everything, and people think it is dangerous to go anywhere right now, including Disney.
My wife and I were in Lancaster PA over the summer. The buffet restaurants were open at 25%, but they could not even fill those limits. We never had to wait for a table. Despite that fact that the businesses were going overboard with their safety requirements, people just were not getting out.
Once safety is established for the vaccine, I think people will want to get it so that they won't be afraid to go out and do things. For those who don't take it, the risk will be on them just like it is for any other disease.
Personally, I expect that we will get the vaccine even having had the disease by early 2022. We have our next cruise booked for then and while I don't think any American business will require vaccinations I am almost 100% certain that the foreign flagged cruise lines will.