Impact of seasonal malaria chemoprevention: a plausibility evaluation of routine data from health facilities in three implementing states in Nigeria

Authors: Ebenezer C Ikechukwu, Ekechi Okereke, Olabisi Ogunmola, Jennifer Chukwumerije, Daniel Emeto, Emmanuel Salifu, Ayodeji Balogun, Chibuzo Oguoma, Emmanuel Shekarau, Nnenna Ogbulafor, Eoin Cassidy, Christian Rassi, Olusola Oresanya, Chukwudi A Nnaji

Following the introduction of seasonal malaria chemoprevention, uncomplicated malaria cases fell by half overall; however the study identified significant variations in the level of reduction between the three implementing states.

Background 

Seasonal malaria chemoprevention (SMC) has been recommended by the World Health Organization since 2012 for eligible children in areas where malaria transmission is highly seasonal and intense. By 2024, SMC had been successfully implemented in all 21 eligible states in Nigeria. Given this widespread implementation, there has been increasing interest in understanding the impact of the intervention under programmatic conditions. This study assessed changes in malaria case incidence and related epidemiological outcomes among the target population of children aged 3–59 months in three SMC implementing states in Nigeria. 

Methods 

The study employed a pre-post plausibility evaluation design. Data from routine health management information systems were extracted from selected health facilities to compare the incidence of parasitologically-confirmed uncomplicated malaria cases and secondary outcomes among children aged 3–59 months within the catchment populations of participating health facilities. Mixed-effects, multilevel, negative binomial regression models were used to estimate the impact of SMC on outcomes of interest between the pre-SMC period (2021) and SMC period (2022).

Results 

Data were collected in 36 health facilities: 12 each in Kogi state, Oyo state and the Federal Capital Territory. The mean incidence of uncomplicated malaria was 20 cases per 1,000 children aged 3–59 months in 2021, and nine cases per 1,000 children in 2022. After accounting for potential confounders, malaria incidence was 50 percent (95 percent confidence interval [CI]: 39–60) lower in the SMC period compared with the pre-SMC period. The level of reduction varied across the three study locations, with the greatest impact in Oyo state and no evidence of impact in Kogi state. Incidence of all-cause fever per 1,000 children was 29 percent (95 percent CI: 14–41) lower in 2022 compared with 2021. Observed levels of severe malaria and attributable deaths were too low to measure the impact of SMC on these secondary outcomes.

Conclusion 

The study found significantly lower levels of incidence of uncomplicated malaria cases following the introduction of SMC, although the magnitude of impact varied notably across locations. It thus provides evidence on the potential impact of the intervention under programmatic conditions, while underscoring the need to improve both the quality of SMC delivery to maximise impact, and the quality of routine data sources to enhance their utility for evaluating SMC impact in eligible settings.

Citation: Malaria Journal, 2025; 24: 396