Theoretically if we return to "life as normal" once the vaccine has been distributed to everyone who wants it, but a significant portion of high risk individuals do not get vaccinated, it could overwhelm our hospitals.

That said, I think the fears about many people refusing the vaccine are completely overblown. All of the folks who I've talked to who are concerned about the vaccine have expressed willingness to get it after it has been out for a few months without major side effects. They wont qualify to be first in line anyways, so they'll have to wait regardless.

No vaccine is ever 100%, you will see that some vaccinated people do get sick. In addition you have people that can't be vaccinated, these are still at risk. But if you vaccinated enough people, the successful vaccinated will act as a kind of firewall and hinder the sickness from effectively spreading.

But comments above state that the vaccine doesn't effect spread. If that's true, then vaccinating everyone would not address any of those points.

It hasn't been proven to affect spread (because that wasn't tested for). But it's generally assumed it does to at least a degree.

It's also much harder to test spread. You'd have to do repeated follow-up of all participants with frequent testing. When you have 40,000 participants, that's a significant concern. Trials like these are called "large, simple trials" since at that scale it's impractical to have a complicated study design at that scale. In addition to the pure expense, it's difficult to comply consistently with the protocol if it's complicated and you need to implement it at dozens or hundreds of sites. And recruiting people becomes harder and harder as you need additional follow-up, and attrition is higher (and likely biased: you're more likely to take your test if you think you might be sick).

So it's entirely reasonable to just study symptomatic cases in these trials.

IIUC, you want to vaccinate everyone to get actual herd immunity as quickly as possible so the virus can't spread before it has mutated into different strains.

The more of the population unvaccinated, the larger population available for new strains to generate in, the higher probability of multiple strains.

It's not guaranteed the current vaccines inoculate against new strains, so you could be right back at square one next winter, with a new virulent strain.

There's probably a good chunk of people who want neither covid nor the vaccine. Life's messy like that.

For the same reason everyone who buys a motor vehicle has to buy one with a catalytic converter. The actions of every individual affect society as a whole.

Because we can't be bothered to go after cruise ships? https://news.ycombinator.com/item?id=19016428

Why is your reply framed as an exclusive "or" choice?