As I mentioned earlier on Phuket, the largest island in Thailand the SDF using CNVR, has effectively eliminated rabies but the threat still exists via the importation of dogs to market to be sold as pets..
In some countries small (usually uninhabited) islands have have had invasive species such as rats eliminated, but they then have to be constantly vigilant to make sure they don't return....usually via humans.
This is still in effect a form of the vacuum effect.
It is also why sterilisation and vaccination are so important as ot prevents the vacuum effect and thrn reduces breeding.