Neither vaccine was fully sterilising. In fact current US CDC advice if going to a country with a polio outbreak is to get a booster.
In both those cases the vaccines just blunted the transmission rate enough for r0 to drop below 1. We were also lucky that the responsible viruses had very stable mutation rates & no animal reservoirs unlike SARS-CoV-2. That meant they mostly died out over time once the transmission rate was reduced.
In both those cases the vaccines just blunted the transmission rate enough for r0 to drop below 1. We were also lucky that the responsible viruses had very stable mutation rates & no animal reservoirs unlike SARS-CoV-2. That meant they mostly died out over time once the transmission rate was reduced.