Vaccination with RTS,S induces antibodies against circumsporozoite protein (CSP), which is expressed by sporozoites, the infective form of Plasmodium that mosquitos transmit. During infection in unvaccinated individuals, sporozoites travel to the liver, where they move through hepatocytes and differentiate to hepatic merozoites. CSP is expressed in the early liver stages, but not by liver stage merozoites. Antibodies to CSP following RTS,S vaccination immobilize the sporozoites, thereby preventing infection of hepatocytes. RTS,S-induced protection from infection and severe disease wanes over time and correlates with the level of anti-CSP antibodies. RTS,S-induced immune responses do not interfere with the infectivity of Plasmodium gametocytes to mosquitoes. Even following vaccination, most children will carry parasites that will infect mosquitoes; thus, transmission in the population will remain unchanged. Image adapted from Raphemot et al. (19).