Adherence to Seasonal Malaria Chemoprevention and Malaria Positivity among Under- Five Children in Ogbomoso, Oyo State, Nigeria

Background Seasonal malaria chemoprevention (SMC) is an effective strategy for malaria prevention in high-transmission settings with marked seasonality. Low SMC coverage and adherence may contribute to disease burden and undermine effectiveness. This study examines SMC adherence, correlating it to malaria positivity among under-5 children in Ogbomoso, Oyo State, Nigeria. Methods A total of 1,257 under-five children were recruited for this study from two SMC cycles, comprising 804 who received five monthly doses of SMC during the peak of the 2023 and 2024 rainy seasons (June to October), and 453 non-SMC controls. Socioeconomic characteristics and adherence to SMC uptake were collected using a structured questionnaire, while malaria positivity was assessed with malaria Rapid Diagnostic Test (mRDT). Data was analyzed, and the results were presented in proportion. The odds of malaria positivity rate were assessed, and the p-value was set at p  < 0.05. Results The prevalence of malaria among the SMC and non-SMC groups was 16.8% and 15.2% respectively. Children aged 13–36 months had higher odds of malaria infection (OR = 2.05, 95% CI: 1.13–3.74) in both arms. Socioeconomic factors such as living in shared apartments were associated with increased risk (OR = 2.32, 95% CI: 1.36–3.95), and non-use of insecticide-treated nets was linked to higher odds (OR = 1.60, 95% CI: 1.08–2.38) of malaria infection. Adherence to the complete SMC regimen was high (96.8%), with rural residents exhibiting significantly higher adherence than urban residents (p = 0.001). Conclusion These findings underscore the need to expand SMC to high-transmission settings during the peak of malaria transmission to reduce disease burden.