When the immune system creates antibodies, they basically hug the spike protein and build antibodies on every nook and cranny they can find a way to bind an ant

When the immune system creates antibodies, they basically hug the spike protein and build antibodies on every nook and cranny they can find a way to bind an antibody. These regions are called epitopes, and the immune system creates many antibodies for each invader. If the spike protein mutates, it means that the structure of the spike is different. Obviously the spike can't change too much, because it needs to still be able to latch onto cells, and many changes would be irrelevant. Even if one antibody suddenly stops working because of a slight shift in the protein, there are other antibodies targeting different parts of the protein that would still be effective. Only if the spike changes so dramatically that literally none of the antibodies you had before are relevant anymore. That's why it's not super expected that we'll get a version of the virus that these vaccines won't at least produce some antibodies against.