Herd protection against <i>Plasmodium falciparum</i> infections conferred by mass antimalarial drug administrations and the implications for malaria elimination

The global malaria burden has decreased over the last decade and many nations are attempting elimination. Asymptomatic infections aren’t normally diagnosed or treated, posing a major hurdle for elimination efforts. One solution to this problem is mass drug administration (MDA), which is dependent on adequate population participation to disrupt transmission. There is little empirical evidence regarding the necessary threshold level of participation. Here we present a detailed spatiotemporal analysis of malaria episodes and asymptomatic infections in four villages undergoing MDA in Myanmar. Individuals from neighborhoods with high MDA adherence had 90% decreased odds of having a malaria episode post-MDA, regardless of individual participation, suggesting a strong herd effect. High mosquito biting rates, living in a house with someone else with malaria, or having an asymptomatic malaria infection were also predictors of clinical episodes. Spatial clustering of non-adherence to MDA, even in villages with high overall participation, can frustrate elimination efforts.