yes, likely the immunogenic ones are cumulative but some risks might be transient or situational and one could try to assess if those risks are present or absent at each injection event. Let's say the first vaccine reactivated shingles, would the second one do so again? On the other hand, say the lipid nano particle has some unknown level of toxicity to a part of the body where it's accumulating. Repeated exposure will be cumulative risk and not situational.