Genotypic analysis of Plasmodium falciparum malaria parasites in a clinical trial of RTS,S vaccination in combination with seasonal malaria chemoprevention

A recent clinical trial showed that the combination of these interventions provided substantial protection against malaria over a five-year period. We performed amplicon-based genotyping of highly polymorphic parasite antigens within 1530 samples from this clinical trial.

We evaluated the complexity of infection within these samples, finding that participants who received both interventions had less complex infections (fewer genetically distinct parasite strains) than participants who received either intervention given alone. We also evaluated the prevalence of parasites matching the vaccine construct CSP, at the level of haplotypes, epitopes, and individual amino acid changes. We found no significant differences in the prevalence of vaccine-matching alleles between vaccinated and unvaccinated groups.