Mass Drug Administration Reduces Malaria Incidence but Requires Sustained Effort in Southeast Senegal

Malaria elimination progress in Africa has stalled despite scale-up of standard control interventions. Mass drug administration (MDA) shows promise for reducing transmission, but evidence is limited for low-to-moderate transmission settings. To inform clinical practice, we interviewed study authors Michelle Hsiang, MD, MS, and Michelle E Roh, PhD, for expert insights on their recent trial.

Coverage of MDA improved across rounds, with 74%, 79%, and 81% of eligible participants receiving treatment in cycles one through three. No serious adverse events were reported, confirming safety. The adjusted reduction in malaria incidence was approximately 55% (95% CI, 28 to 71) during the intervention year but declined to 26% (95% CI, –17 to 53) post-intervention. Malaria incidence during the post-intervention transmission season remained 126 cases per 1000 population in the intervention arm versus 146 cases per 1000 in controls.¹

This open-label, cluster-randomized controlled trial in southeast Senegal randomized 60 villages with moderate-to-low seasonal malaria transmission (60–160 cases per 1000) to either three cycles of MDA with dihydroartemisinin–piperaquine plus single low-dose primaquine at 6-week intervals or standard seasonal malaria chemoprevention (SMC) with sulfadoxine–pyrimethamine plus amodiaquine every 4 weeks. The primary endpoint was Plasmodium falciparum incidence in the post-intervention season (July–December 2022). Safety, coverage, and incidence during the intervention year were secondary outcomes.¹
Hsiang and Roh emphasized that “in our study setting, where malaria transmission was moderate-to-low and highly seasonal and coverage of standard malaria control interventions (eg, vector control, surveillance, case management) was high, three rounds of MDA with dihydroartemisinin-piperaquine and single low-dose primaquine rapidly reduced malaria incidence by ~55%.” Although, “this effect was not sustained upon discontinuation of MDA, with none of the villages reaching pre-elimination levels (<5 cases per 1000 population) in the subsequent transmission season.”¹

Regarding future malaria control strategies, they recommend: “Ensure that the number of MDA rounds administered covers the full transmission season. It is likely that, in our study, partial coverage of the transmission season contributed to the weak sustained effect in the post-intervention year.” Furthermore, programs should “aim to reach >80% coverage of the population (supported by WHO recommendations), which may require strong community acceptance and engagement by the local health and administrative officials.” They also noted, “MDA is costly and resource-intensive and may require sustained commitment over several years to maximize benefits.”¹

On challenges to sustaining MDA’s impact, their recommendations include: “MDA will likely need to be repeated annually over several years until malaria incidence drops to low levels, at which point programs can consider transitioning to more targeted strategies such as focal MDA.” They stress that “to effectively reduce the parasite reservoir, the timing and frequency of MDA rounds should cover the entire transmission season.” Finally, “community sensitization and engagement are critical to reaching high coverage,” with additional efforts needed “to engage groups who may be less likely to participate in standard chemoprevention campaigns, including adults, adolescents, and highly mobile populations.”²
The study’s open-label design and geographic focus limit generalizability. The diminished effect after cessation of MDA highlights the challenges of achieving sustained malaria control with limited intervention rounds.¹
MDA with dihydroartemisinin–piperaquine plus single low-dose primaquine is safe and reduces malaria incidence significantly during active administration in a moderate-to-low transmission African setting. Although, Hsiang and Roh conclude, “MDA will likely need to be repeated annually over several years until malaria incidence drops to low levels, at which point programs can consider transitioning to more targeted strategies such as focal MDA.” Successful malaria control via MDA requires optimized timing, full seasonal coverage, and strong community engagement to maintain gains.¹

References

1.Effect of mass drug administration on malaria incidence in southeast Senegal during 2020–22: a two-arm, open-label, cluster-randomised controlled trial. Ba, El-hadji Konko Ciré et al. The Lancet Infectious Diseases, Volume 25, Issue 6, 656 – 667. June 2025. Accessed July 7, 2025.

2.Brady OJ, Slater HC, Pemberton-Ross P, et al. Role of mass drug administration in elimination of Plasmodium falciparum malaria: a consensus modelling study. Lancet Glob Health. 2017;5(7):e680-e687. doi:10.1016/S2214-109X(17)30220-6