You're missing the picture here... vaccinated people think they are now magically immune. However, they can still get it, spread it, and die from it. An unvaxed person when they get covid is like - "oh shit, I'm sick, I better stay home so other people don't get it". Where as vaxxed persons won't know they have it, or think they have just a head cold, and can spread it to hundreds of people within a couple days.