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 !!
Watch this short video