Seasonal malaria chemoprevention effectiveness and drug resistance in Plasmodium falciparum: a matched parallel cohort study, Kenya.

Objective: To evaluate seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine in a semi-nomadic community in north-western Kenya, and to examine the relationship between parasite resistance and breakthrough infections. Methods: gene substitutions associated with sulfadoxine-pyrimethamine resistance. Findings: gene mutations were more common in the intervention than non-intervention cohort and became more frequent as the number of treatment cycles increased. Conclusion: Seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine was associated with substantial protection against malaria in children in an area where sulfadoxine-pyrimethamine resistance was common. Treated children were more likely to harbour resistant parasites.