Despite increased malaria control measures and falling malaria cases, Plasmodium vivax persists. The reasons for the greater persistence of P. vivax relate to its unique biology, most importantly its ability to relapse from long-lasting, dormant liver stages (hypnozoites). There are no diagnostic tests for hypnozoites and the only currently available drug to clear hypnozoites is primaquine which can be dangerous or ineffective depending on a person’s genetics. By studying the genes of people in different countries we will determine the risk and efficacy related to anti-malarial and anti-hypnozoite treatment in that region. With this work we can make best use of the drugs we currently have.