The way I understand it, even after being vaccinated, you can still catch covid-19, but you won't have severe symptoms. Some of the vaccine manufacturers are claiming 100% protection from hospitalization from symptoms -- a claim of which I'm highly skeptical. Maybe 99%, but nothing is 100% effective. We shall see, I guess.
So if you're vaccinated, covid-19 is about a dangerous to you as the flu, but you can still spread it, and if you spread it to unvaccinated people, it can put them in the hospital or kill them. Eventually, everybody is going to catch covid-19, but it's only going to kill the unvaccinated.