And every time you generate an immune response you are honing your natural receptors so although they are more specific to the specific virus at hand, they lose general response, so this can backfire for example if you over-vaccinate with the wrong strain of flu and this one year the flu changes direction, mutationally.
this is called “original antigenic sin”
Wait, so what are we supposed to do. If you over vaccinate is bad, if you under vaccinate is bad, but if you vaccinate a little bit you can end up on the wrong strain. Great! /s