There's a long-standing gap in medical knowledge about what happens if you give someone "too much" vaccine– basically, nobody actually knows if that's even a thing, let alone what it would look like, because there's no ethical way to find out. This has been true pretty much since vaccines were invented. And I'm giving you that context because I want you to appreciate that a tremendous number of scientists and doctors wish they had that knowledge, if only there was some way to get it without turbo super ultra ethics violations.
Hey remember how when the COVID vaccine first came out and various powers told people to go get it, a black market sprung up wherein antivaxxers would pay to get out of shots, sometimes via simple document forgery... but sometimes via a stand-in getting the shot in their name?
Prosecution in Germany found a guy who, in over the course of 29 months, got 217 COVID vaccinations. (That's an average of 7.48 vaccinations per month.) When he got caught he volunteered for medical scientists to inspect him. The study has been published. tl;dr he's fine. Science emphatically does NOT recommend that you do this... but detectable anti-spike IgG in his saliva aside there's otherwise nothing of note, he's fine.
