John is applying a genetic approach in two stages. First, he will identify genetic variants that reliably alter iron status in African children by conducting a genome-wide association study. He will then use the identified genetic variants in a Mendelian randomization framework to infer whether iron status is causally associated with risks of severe infection and deaths. This work has major public health implication since the question of iron and infection risk is an old one and has left a longstanding dilemma in public health regarding the safety of iron supplementation