Antibodies are LITERALLY the point. It’s the mechanism by which our immune system identifies pathogens and triggers an immune response to them. If they diminish, your immune system is slower to respond and less effective at doing so. If they’re gone, it’s a of your immune system has never seen the pathogen before and has to adapt from zero again. Vaccines are a way to arm you with those antibodies without as much risk either from genuine infection or your immune system killing you in the attempt to figure out how to kill the new pathogen.

TL;DR: Vaccine=Antibodies=Good