One of the mechanisms behind the slow kill may be this now recorded shift in antibody cell type from normal IgG(1) ---> IgG4. When your immune system starts forming IgG4 type immunoglobulins, it's essentially tapping out due to overstimulation by a given antigen. Oh, the wonders of turning our cells into mRNA epitope factories over, and over, and over again, discussed in this new paper out of Germany ; https://www.medrxiv.org/content/10.1101/2022.07.05.22277189v1.full.pdf "Class switch towards non-inflammatory IgG isotypes after repeated SARS-CoV-2 mRNA vaccination"