While 20% of the population resisted the trial, it's not really because they're immune/resistant to the trial itself. It's not a viral, chemical or bacterial effect. What they're doing is a whole lot more clever, let me quote the article:
"From November 2017 to June this year, non-biting male Aedes aegypti mosquitoes sterilised with the natural bacteria Wolbachia were released in trial zones along the Cassowary Coast in North Queensland.
They mated with local female mosquitoes, resulting in eggs that did not hatch and a significant reduction of their population."
In theory all they have to do is keep releasing these males and hopefully eventually all the female vectors will have mated with these introduced males and that's it.
"From November 2017 to June this year, non-biting male Aedes aegypti mosquitoes sterilised with the natural bacteria Wolbachia were released in trial zones along the Cassowary Coast in North Queensland.
They mated with local female mosquitoes, resulting in eggs that did not hatch and a significant reduction of their population."
In theory all they have to do is keep releasing these males and hopefully eventually all the female vectors will have mated with these introduced males and that's it.