In a research article published April 3 in the online, open-access journal PLoS Biology, Prof. Sylvia Cremer and colleagues at the Institute of Science and Technology, Austria show how micro-infections promote social vaccination in ant societies. Like crowded megacities, ant colonies face a high risk of disease outbreaks. These are kept in check by the ants' social immune system—a set of collective hygienic behaviours and adaptive changes in interaction frequencies that acts in conjunction with the physiological, innate immune system of colony members. Prof. Cremer and colleagues now unravel how taking care of sick ants promotes disease protection in their group members. They also discuss their findings in the latest edition of the PLoS Podcast (http://blogs.plos.org/plospodcasts/).