A model from the University of Washington predicts that new COVID-19 cases and deaths will drop to zero shortly after July 1: https://covid19.healthdata.org/projections
I assume that's because the virus runs out of new people to infect, if people who have had it before can't get it again, and if we assume it doesn't mutate.
But then I don't understand what is the point of developing a vaccine that won't be ready for 12-18 months anyway. What does it achieve, if all of the deaths from COVID-19 will have already occurred by this July? And if the reason the deaths level off in July is because so many people have the antibodies by then that we have herd immunity, then who is the vaccine for?
I understand the virus could mutate so that people who have antibodies from the current version will not be immune. But if the eventual vaccine is going to be based on the current version, doesn't that mean that if it mutates, people who get the vaccine won't be immune either?
I can think of some possible answers that would make sense (by which I only mean they would make logical sense as an answer; I don't mean that they make scientific sense):
1) The UW model represents a rogue view and people are working on the vaccine because they don't think it's correct.
2) Even if we achieve herd immunity at 75%, the vaccine is to protect the remaining 25%. (I would call this a special case of #1, contradicting the UW model, because it seems to assume there is a significant number of preventable deaths lying to the right of July 2020.)
3) People who get the SARS-CoV-2 virus will only be immune to the current version, but the vaccine can be developed in a way that it might also provide immunity against other mutated versions.
4) The vaccine is not going to be ready in time to make a difference against the current SARS-CoV-2, but we're working on a general strategy for identifying any mutated strains that might appear next year, so that we can respond quickly with a vaccine, similar to what we do with the flu.
5) Even though we think our bodies will retain the antibodies from SARS-CoV-2 indefinitely, there's a chance that they might not (similar to norovirus), so the vaccine is to cover that possibility.
Or something else?