Extension of seasonal malaria chemoprevention to older children: a pragmatic comparative study in two health districts in the Zinder region, Niger.

contextSeasonal Malaria Chemoprevention (SMC) based on sulfadoxine-pyrimethamine (SP) and Amodiaquine (AQ) has been recommended by the WHO since 2012 for areas where malaria is endemic but seasonal. It consists of administering to healthy children under the age of five years a full three-day course of treatment every month for three to five months during the transmission season. However, in these areas, retrospective data on the burden of malaria among children aged 5 to 10 years could justify extending this strategy to this class of age. This study was conducted to evaluate the public health effectiveness of this extension in Niger.

methodsWe conducted a retrospective comparative observational study using routine DHIS2 data collected from two health districts in the Zinder region (Damagaram Takaya and Matameye) over a 36-month period (2021-2023). The study compared malaria trends between one district that implemented SMC extension to children aged 5-10 years (Damagaram Takaya) and another district where SMC remained restricted to children under 5 (Matameye). In each district, five health facilities were selected using simple random sampling from the official list of operational health facilities provided by local health authorities. The selected facilities were used as sentinel sites for extracting data on fever episodes, uncomplicated malaria, severe malaria, and malaria-related deaths, stratified by age group. This design enabled the comparison of malaria incidence patterns before, during, and after transmission seasons between districts with different SMC coverage strategies.

resultsFrom 2021 to 2023, children aged ≥ 5 years showed a higher incidence of uncomplicated malaria than younger children, particularly in 2021 when the incidence reached 33.34 per 1,000 compared with 12.45 per 1,000 in <5-year-olds in Damagaram Takaya. In Damagaram Takaya, a significant decrease in both uncomplicated and severe cases occurred in 2023, following expansion of SMC to this age group. In Matameye, severe cases decreased as well, though there was no significant change in uncomplicated cases. In the same district, marked disparities were found between health facilities. Among children under five years, severe malaria cases were more frequent in Matameye, with peaks observed in 2021. Despite a slight decrease in 2023, there was no significant variation in uncomplicated cases during the study period in this district. Extending SMC to children aged 5 years and older was associated with a gradual decline in the incidence of uncomplicated and severe malaria in the target district, but not in the control district. However, this new strategy did not result in a delay in the peak of transmission that would have been induced by the destruction of the parasite reservoir. There was also considerable variability in the data recorded by each health facility.

conclusionThese results underscore the positive impact of expanding SMC to older children and the importance of adapting control strategies to local circumstances. SMC is an effective, low-cost strategy for preventing malaria cases in children of all ages. CLINICAL TRIAL NUMBER: Not applicable.