It takes some time for the vaccination to replicate the antibodies so you can still come down with symptoms even if you've been vaccinated. To be even partially effective it will take a couple of weeks. My understanding is that once the antibodies are replicated you either won't show symptoms or your symptoms will be far less severe but you can still carry the virus meaning you can pass it on to someone not vaccinated. Simply put, the vaccination won't eliminate you from getting the virus However, once "effective" you won't get the really bad symptoms or hopefully no symptoms.

If your concerned talk to your Doc about this stuff. Bottom line is it takes a while after vaccination to be effective and even then you will carry the virus that can be passed on. But I'm assuming your Doctor has explained this stuff to you.