What do you mean?
The mRNA shots did not prevent any infection, and in fact those who took the mRNA shots got covid multiple times on average.
Which means the mRNA not only provided zero immunity, but somehow removed the natural recovery immunity people who did not take the shot had.
Covid did not stop until way over the 72% infection rate that was predicted to stop it through herd immunity.
So then clearly the mRNA did not at all reduce the epidemic duration.