I've seen reports that say that if you have Covid, you transmit it as easily as anyone else, regardless of vaccination status.

That is why we see so many people saying that the vaccines don't prevent you from spreading it.

However, if you're vaccinated, you're less likely to get it in the first place, so from a standing start, you're less likely to transmit it. And since at some point everyone was covid-free, this is the important scenario.

Nobody who knows they have the virus should knowingly go near another person except in an emergency. Nothing you do will protect that other person.