" Preliminary data indicates the vaccines do prevent transmission as well as negating the effects of the disease. How long it’s effective for is yet to be determined, however the vaccines seem to be doing better than expected."
evidence from the UK (now 32.3 million first jabs and 8.1 million second jabs) shows that the even a single shot reduces transmission (as well as infection) and lasts at least 3 months, a second jab improves things and after 6 months show s no sign of diminution in effect. They also seem to be effective against the new variants. There are indications that the Pfizer and the Astra Zeneca trigger different parts of the immune system and they are running trails to see if, in the long run, getting a mixture of vaccination types may up the protection even further.
The dramatic fall in cases and hospitalisations was initially due to the severe lockdown but now you can see the vaccine affect - old people are no longer the majority of either hospital cases or new cases