An important, as of yet unresolved question, is whether those changed vaccines will lead to the generation of new antibodies vs. a boost of the existing ones, a phenomenon called original antigenic sin. Fingers crossed...
It's basically the immune system keeping and using an old weapon that is no longer effective just because the intruder has the same haircut as his great great grandfather.
There is a natural balance, between host and virus and population, that keeps the mutability and lethality in check.
Basically a natural kind of population control. Vaccines and technology in general do in a sense change this dynamic.
It's possible that the immune system becomes decoupled and evolutionarily atrophied when an artificial immune system becomes the primary defense.
I don't have a good enough bio background to give a great answer here. But I can reference a paper that has provoked all manners of thoughts on my end [1].
So if you take a read through that paper, perhaps you can begin to wonder what I am so nervous about. If vaccines previously mediated human evolution to some degree, what's going to happen when humans begin to seize control of that mediator? What's the runaway feedback loop look like?
[1] "Role of viruses in human evolution" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7159740/