Covid vaccines are not designed to stop Sars-Cov2 infections, but rather suppress the symptoms of Covid 19.
(Sars-Cov2 is the infection & Covid19 is symptoms that come from Sars-Cov2)
After you get a covid vaccine you can still have the infection and spread it. You just may not have the symptoms. This can make you an asymptomatic carrier of the infection !!