Vaccines never quite prevent infection. What they do is give the immune system a head start so they can overtake the infection early. Hopefully early enough to prevent symptoms, and ideally early enough to prevent transmission.
But just how early the immune system can win will depend on the strength on the immune reaction and the specifics of the virus. So for this specific one we don’t yet know whether it’s early enough to prevent subsequent transmission.
For example if transmission would require coughing and you never develop a cough, then there probably won’t be much transmission. But the potential for pre-symptomatic transmission suggests that it won’t be that simple, and while in theory this should reduce transmission it probably won’t eliminate it entirely.
But just how early the immune system can win will depend on the strength on the immune reaction and the specifics of the virus. So for this specific one we don’t yet know whether it’s early enough to prevent subsequent transmission.
For example if transmission would require coughing and you never develop a cough, then there probably won’t be much transmission. But the potential for pre-symptomatic transmission suggests that it won’t be that simple, and while in theory this should reduce transmission it probably won’t eliminate it entirely.