Despite significant progress in malaria control in sub-Saharan Africa, the disease remains a major public health concern, particularly among children living in areas with highly seasonal transmission patterns. Seasonal malaria chemoprevention (SMC), utilizing the combination of sulfadoxine–pyrimethamine and amodiaquine, has emerged as an effective strategy for reducing malaria-related morbidity and mortality.

Since its endorsement by the World Health Organization in 2012, SMC has been widely implemented across West African countries, including Senegal, with substantial reductions in malaria incidence reported [1,2,3,4,5,6,7,8]. More recently, the expansion of SMC recommendations to include older children reflects evolving evidence regarding malaria risk across different age groups. Notably, studies conducted in Senegal and Mali indicate that children aged 5–10 years remain particularly vulnerable [2,9,10,11,12,13].

However, the long-term success of SMC programs is contingent not only on their efficacy but also on the quality of implementation, the coverage achieved, and the tolerability under real-world conditions. Evidence from clinical trials, while reassuring, does not always fully capture the operational challenges associated with large-scale program deployment.

In Senegal, although SMC has been implemented for over a decade, comprehensive data on the scale-up process, coverage levels, and long-term tolerability remain limited—especially in light of the expanded target populations. Furthermore, while the adverse events associated with SMC are generally mild and transient, they may impact community adherence and overall program performance.

Additionally, emerging observations suggest potential variations in the occurrence of adverse events based on individual characteristics, such as sex, raising important questions related to pharmacovigilance and equity in intervention outcomes.

In this context, there is a clear need for robust and integrated evidence to evaluate the multiple dimensions of SMC implementation. This study was thus initiated to meet this requirement. Its objective was to describe the different stages of the scaling-up process, to determine coverage rates and to assess tolerance during the first ten years of implementation in Senegal.

This study is a retrospective and secondary analysis of routine data from the National Malaria Control Programme (NMCP) in Senegal. It focused on information regarding SMC in Senegal from 2012 to 2021, covering the periods of its adoption, pilot implementation, and scaling up in parts of the country that meet the SMC eligibility criteria [1] (Figure 1).

To describe the key stages in the rollout of this malaria chemoprevention strategy in the country, reports from the various meetings that led to decisions on adoption, initial pilot-phase implementation and scaling up were analyzed. The data on SMC administration coverage analyzed in this study were drawn from all annual epidemiological bulletins [14,15,16,17,18,19,20,21] and official feedback reports for each SMC administration round under the NMCP covering the study period.

Only SMC coverage (proportion of children treated among all children recorded in the target population) data by administration round, reported in these bulletins, were extracted using Microsoft Excel (version 16.78.3) and subsequently analyzed using RStudio (version 2026.01.1+403).

SMC coverage rates were expressed as percentages and summarized by administration round and by implementation region across the study years. In addition, mean annual national coverage rates were compared using analysis of variance (ANOVA).

The study period was divided into two distinct phases. The first (2013–2017) corresponded to the period during which only the first dose of sulfadoxine–pyrimethamine plus amodiaquine (SPAQ) was administered under directly observed treatment (DOT) by community health workers, while the second and third doses were administered at home by caregivers on days 2 and 3. This phase also preceded the suspension of SMC implementation in 2018 due to nationwide health worker strikes. The second phase (2019–2021) corresponded to the resumption of SMC, during which all three doses were administered under directly observed treatment by community health workers. Mean coverage rates between these two periods were compared using Student’s t-test.

The level of statistical significance was set at p < 0.05 for both ANOVA and the t-test.

To assess the tolerability of SMC, adverse event reports submitted by regional medical authorities to the national poison control center responsible for causality assessment were reviewed. Data on adverse events were also extracted from annual epidemiological bulletins and post-campaign feedback reports for each administration round. All collected data were entered into Microsoft Excel (version 16.78.3). The number of reported adverse events (AEs) was extracted from these documents, and annual totals were calculated by summation. The annual AE incidence was then computed by dividing the total number of AEs by the total number of children treated during the corresponding year. Incidence rates were compared to the reference year 2013 (year of pilot phase) using the χ² test with Yates’ continuity correction. Analyses were done using RStudio (version 2026.01.1+403).

This study provides a comprehensive analysis of the first ten years of seasonal malaria chemoprevention (SMC) implementation in Senegal. It documents the scale-up process, coverage achievements, and tolerability profile. Several limitations should be acknowledged: reliance on routine programmatic data subject to reporting issues, absence of 2018 data, potential overestimation of coverage due to denominator inaccuracies, and lack of clinical outcome data.

The findings of this study demonstrate that SMC has been successfully scaled from an initial pilot in two districts in 2013 to nationwide coverage in eligible regions, with sustained high coverage rates and a very low overall incidence of adverse events. These results reinforce the feasibility and effectiveness of community-based SMC delivery within a routine health system context [2,4].

The rollout of seasonal malaria chemoprevention (SMC) in Senegal over time followed the World Health Organization (WHO) recommendations for implementing this strategy [1,2]. Indeed, after a pilot phase with two administration cycles in 2013 in the three health districts of the Kédougou region and in Dianké Makha (Tambacounda), the intervention was progressively expanded to other eligible areas, with the number of cycles adapted to the local context. The continuous evaluation of this strategy also led to the removal of the Sédhiou region in 2020 from SMC-eligible areas, as it no longer met the eligibility criteria.

The non-administration of seasonal malaria chemoprevention (SMC) in 2018 due to a health worker strike highlights the fragility of our health system. The absence of alternative mechanisms in such situations threatens all the efforts made to sustain the gains achieved by the country, particularly in malaria control. This observation is especially relevant given the growing emphasis on health system resilience [3,13]. Moreover, this study demonstrates, through the coverage rates achieved after this interruption, the capacity of the Senegalese health system to recover and rebound [4].

The transition from DOT of only the first dose to three-day DOT represents a major programmatic shift and further reflects the continuous evaluation of SMC and the commitment to ensuring that children receive the full course of treatment. This change may also explain the increase in adverse event (AE) reporting following the introduction of three-day DOT, as closer supervision by community health workers likely improved the detection and reporting of AEs [11,12].

CPS coverage rates in Senegal during the study period varied over time and across regions, but consistently hovered around the 95% target, as shown by the national annual averages, which ranged from 91.7% to 97.5%. The achievement of these coverage levels could be explained by community engagement, door-to-door delivery, strong political commitment, and thorough training of CHWs [8,14,15,16]. Although coverage levels were generally high, they varied across years and regions, with both declines and increases observed. The declines could be explained by the implementation of the full three-day directly observed treatment (DOT), suggesting a trade-off between treatment completion and coverage efficiency [17]. They may also be attributed to the expansion of the program to new regions with limited experience in implementation, as well as the lingering effects of the 2018 health worker strikes. Coverage rates exceeding 100% suggest potential inaccuracies in target population estimates, a common phenomenon in administrative coverage data [18].

Senegal’s coverage rates (91.7–97.5%) compare favorably with those of other West African countries. Niger achieved 85.7% in 2016 [6], the ACCESS SMC project reported average monthly coverage of 76.4% in 2015 and 74.8% in 2016 across seven countries [23], and Mali achieved 77% average first-dose coverage [24]. The door-to-door delivery approach in Senegal likely explains these higher rates [14,25].

The overall AE incidence in this study was very low and the majority were minor with only 19 major AEs reported over ten years, all of which resolved after hospital care. These findings are consistent with previous studies in Senegal, which reported AE incidences of 0.1–0.2% and very few serious events [14,19]. Annual AE incidence ranged from 0.01% to 0.33%. The peak observed in 2015 coincides with program expansion, while the increases in 2019 and 2020 align with the transition to three-day DOT.

Comparable findings have been reported in other countries. In Niger, no serious AEs were reported in 2016 [6], and in Mali, 131 AEs were reported in 104 children between 2015 and 2016, with the majority being mild [20,21].

The geographic distribution showed higher AE numbers in Kaolack, Sédhiou, and Kolda, likely reflecting the larger number of children treated. However, the complete absence of reported AEs in certain regions despite high coverage suggests underreporting, highlighting the need for strengthened pharmacovigilance [22]. The balanced distribution by sex and age group supports the expanded target population to include children up to 10 years of age [2].

The implementation of SMC in Senegal has been dynamic. It began with a pilot phase before being scaled up in four regions in the south-east of the country. Over the decade, new areas have been added to the SMC program while one area that no longer met WHO eligibility criteria has been phased out. Community involvement, along with a door-to-door strategy, has led to high coverage rates for this well-tolerated strategy in Senegal.