Abstract / Summary
Seasonal malaria chemoprevention (SMC) is an effective strategy for malaria prevention in areas with highly seasonal transmission. However, suboptimal coverage and incomplete adherence may reduce its effectiveness. This study assessed adherence to SMC and its association with malaria positivity among children under five years in Ogbomoso, Oyo State, Nigeria. A community-based, comparative, cross-sectional post-intervention study was conducted in four Local Government Areas (LGAs) of Ogbomoso, Oyo State, Nigeria. A total of 1,257 children aged 3–59 months were enrolled following two annual SMC implementation cycles. Overall, 804 children were recruited from SMC-implementing communities and 453 from non-SMC comparison communities. Malaria infection was determined using malaria Rapid Diagnostic Tests (mRDTs) and Polymerase Chain Reaction (PCR). Data on adherence to the SMC regimen, verified using caregiver SMC cards and socio-demographic characteristics were collected using structured questionnaires. Associations were assessed using bivariate and multivariable logistic regression analyses, with statistical significance set at p < 0.05. Malaria prevalence by mRDT did not differ significantly between SMC (16.8%) and non-SMC (15.2%) communities ( p = 0.524). Although PCR detected a higher prevalence of malaria infection in SMC communities (9.5%) than in non-SMC communities (5.7%; p = 0.0236), this difference was attenuated after adjustment for measured individual-level and study-level covariates. Because the SMC and non-SMC groups were recruited from geographically distinct LGAs, with SMC implementation fully aligned with LGAs, residual community-level confounding cannot be ruled out despite statistical adjustment. Within the study population, children aged 37–59 months had significantly higher adjusted odds of malaria infection than those aged < 12 months (2.47; 95% CI: 1.33–4.60; p = 0.004). Overall adherence to the complete SMC regimen was high (96.8%). Caregiver education was the only socio-demographic factor significantly associated with adherence ( p = 0.031). RDT- and PCR-positive children had higher odds of non-adherence, although these associations were not statistically significant. While a higher crude prevalence of PCR-confirmed malaria was observed in SMC communities, this association was not maintained after adjustment for measured covariates. Given the geographical separation of SMC and non-SMC populations and the inability to adjust for LGA, these findings should not be interpreted as evidence of a causal relationship between SMC exposure and malaria positivity. These findings may reflect underlying population differences, highlighting the need for continued surveillance and complementary malaria control alongside SMC.