This is the kind of confused weak thinking that causes new infections to rise at 150%
Of course vaccination radically reduces the ability of the vaccinated to spread Covid, 90% of them never get it. Sure of the other 10% that might get it some do and wow they can spread it. By the time you get past the IFs vaccination is astoundingly successful but the more vaccinated that are exposed to the unvaccinated the more of those 10% WILL get infected. This seems crystal clear to me and actually I'm surprised at how low the rate of "breakthrough" cases are (I think I heard < 1% but fact check).