The general mechanism is that recognition of the antigen by memory B cells produces a response that also inhibits (non-memory) B cells from reacting to the antigen. So when the antigen has drifted enough that memory B cells still recognize it, but the antibodies are less effective then at that point B cells are actively inhibited by the memory B cells so new and retargeted antibodies are not produced.
(Social media reports aren’t exactly reliable and everything seems to indicate that your chances of serious complications are worse without a vaccine).
Right now, there’s a deadly virus going around and there might not be a “later” for me if I don’t get the vaccine. I think I’ll take my chances with the vaccine. It seems like a no brainer to me.
I don't think this is how this works.
They "see" antibodies sticking to a target, as successful antibodies are presented for replication and refinement. This implies a functional response. If the vaccine antibodies wouldn't work on a new strain, the B cells wouldn't recognize them as suitable candidates.