Relationship between nutritional status and malaria risk among children receiving routine seasonal malaria chemoprevention: evidence from a prospective cohort study in Mali

Background Malnutrition and malaria remain major overlapping causes of morbidity among children in the Sahel, where seasonal malaria chemoprevention (SMC) is widely implemented. This study assessed the relationship between nutritional status and malaria outcomes, and whether SMC exposure influenced nutritional changes during routine implementation. Methods A prospective cohort study was conducted among children aged 3–59 months during the 2024 malaria transmission season in Sirakorola, Mali. Children were enrolled before the first SMC round and followed monthly (July–October) for Plasmodium (P.) falciparum infection by microscopy, anthropometry, and SMC coverage. Clinical malaria incidence was measured through passive case detection (August–November), defined as fever (≥37.5 °C or within 48 h) with parasitological confirmation. Nutritional status was assessed using weight-for-age, height-for-age, and weight-for-height z-scores. Mixed-effects logistic and Poisson models estimated associations between nutritional status, P . falciparum infection, and clinical malaria incidence, adjusting for age, sex, SMC exposure, and follow-up period. Interaction terms assessed whether SMC modified the association between nutritional status and malaria risk. Nutritional changes were assessed using McNemar's test and longitudinal mixed-effects models for MUAC and weight. Findings Of 425 enrolled children, 42.6% were malnourished at baseline. Malnutrition was independently associated with higher P. falciparum prevalence (6.5% vs. 2.6%; OR=2.20, 95% CI 1.21–3.99), and increase clinical malaria incidence (9.1 vs. 6.0 per 100 person-months, adjusted incidence rate ratio=1.82, 95%, CI 1.11–2.97). Malaria incidence was higher during periods without SMC protection (>28 days since last dose). No evidence of interaction was observed between nutritional status and SMC exposure. MUAC and weight increased over the season across all nutritional groups, with no differential trajectories by baseline status. Interpretation Malnutrition substantially increased malaria vulnerability despite high SMC coverage. Nutritional improvements observed during follow-up suggest potential synergistic benefits. Integrating nutrition interventions with SMC delivery could enhance child survival and accelerate malaria control in high burden regions.