While North Americans don’t have to worry about dengue fever, people in the rest of the world do; it kills about 25,000 people each year, and infects about 390 million a year, and the World Health Organization regards it as one of the top 10 threats to global health. 

That is why a recent experiment in Indonesia is almost miraculous, as if (to use pandemic terms) a whole population had achieved herd immunity when only a few people had been vaccinated. But in this case, it’s the mosquitoes that are ‘vaccinated’ using a microbe that spreads quickly and prevents them from being infected by dengue viruses.