THE MOSQUITO Shield spatial repellent significantly reduced malaria infections by one-third in a groundbreaking clinical trial in Kenya.
This innovative study, led by the University of Notre Dame and supported by Unitaid, tested the efficacy of Mosquito Shield, a transfluthrin-based spatial repellent developed by SC Johnson. The product works by releasing an active ingredient that repels and immobilizes mosquitoes when placed indoors. Conducted in Busia County, a high-burden malaria region, the trial demonstrated that spatial repellents, when used alongside insecticide-treated nets (ITNs), offer an additional layer of protection against malaria. The findings mark a pivotal step toward diversifying global malaria prevention strategies, particularly in areas with high insecticide resistance and intense transmission rates.
The cluster-randomised trial involved 58 clusters (29 intervention, 29 placebo) and assessed 3,072 participants over a 28-month period. First-time malaria infections were reduced by 33.4% (95% CI 11.1–50.1; p=0.0058), and overall malaria infections decreased by 32.1% (95% CI 15.9–45.2; p=0.0004) compared to the placebo group. Researchers recorded no significant adverse events linked to the repellent. With estimates suggesting 60 infections could be averted annually for every 100 people protected, the results underscore the potential for substantial public health benefits.
These findings align with earlier studies on spatial repellents but represent the first definitive evidence of their efficacy against malaria in an African context. As a result, the Kenyan Ministry of Health has integrated spatial repellents into its national malaria control strategy, a significant policy shift for endemic regions. Furthermore, trials are underway in Mali and Sri Lanka to evaluate the product’s broader utility against malaria and dengue.
This study provides compelling evidence for incorporating spatial repellents into malaria control programmes worldwide. The results also pave the way for a potential WHO recommendation of this new class of vector control tool, fulfilling one of the two required evidence contexts. Future research should explore long-term deployment strategies, cost-effectiveness, and integration with existing interventions to optimise impact in diverse malaria-endemic regions. For clinical practice, these findings highlight the importance of adopting complementary tools to address gaps in current malaria prevention measures, particularly for vulnerable populations.
Katrina Thornber, EMJ
Reference
Ochomo E O et al. Effect of a spatial repellent on malaria incidence in an area of western Kenya characterised by high malaria transmission, insecticide resistance, and universal coverage of insecticide treated nets (part of the AEGIS Consortium): a cluster-randomised, controlled trial. The Lancet. 2024;405(10473):147-56.
