[NANP]19-5.1. A malaria vaccine field trial in Nigerian children

[NANP]19-5.1 is a recombinant Plasmodium falciparum vaccine consisting of 19 repeats of the sporozoite surface protein [NANP] and the schizont export antigen 5.1. In a previous study, an experimentally infected subject (with a history of malaria exposure and an elevated pre-immunization lymphocyte stimulation index to antigen 5.1) showed parasitaemia but no signs of clinical malaria. In an attempt to find a comparable partially immune population, we tested the vaccine in 194 schoolchildren (6 to 12 years, vaccine and placebo groups of equal size), who already possessed a certain degree of immunity. It was hoped that this immunity would be boosted by the vaccine. During the 12 weeks of observation, no child developed clinical malaria. Analysis of serum taken before and after immunization revealed that, except for eight children, all had considerable levels of antibodies to both antigens. We conclude that the trial should be repeated in younger children who are still vulnerable to clinical malaria.