Spatial repellents: from South Bend to a WHO recommendation, 2025

2025

A new class of protection: The most recent advancement in this section is also the largest in reach. A spatial repellent is a device hung in a room that emits a volatile chemical into the air, keeping mosquitoes from entering, finding and biting the people inside — protection that works in the hours and places where bed nets cannot. The epidemiological proof that the devices work, assembled under the AEGIS project — Advancing Evidence for the Global Implementation of Spatial Repellents — was led by the University of Notre Dame and funded by Unitaid, with Nicole L. Achee as lead principal investigator and scientific director and John P. Grieco among its leaders. The decisive trial, in Busia County, western Kenya, was a cluster-randomized controlled trial run with the Kenya Medical Research Institute and the Centers for Disease Control and Prevention in an area of high transmission, insecticide-resistant mosquitoes and universal bed-net coverage: published in The Lancet in January 2025, it found that homes with the transfluthrin spatial repellent added to insecticide-treated nets suffered first-time malaria infections at a hazard rate 33.4 percent lower, and overall new infections 32.1 percent lower, than homes with nets and a placebo device — the first demonstration of a spatial repellent's protective efficacy in such an African setting, in the paper's own conclusion.

An earlier Notre Dame trial in Indonesia had pointed the same way, with reductions of about twenty-eight percent in first-time and forty-one percent in overall infections in the clusters reported. In 2025 the World Health Organization issued a conditional recommendation for spatial emanators in malaria control, informed by the AEGIS evidence; Unitaid, the funder, called spatial repellents "the first new class of vector control intervention in decades," and the characterization is carried as Unitaid's. The emanator device itself was developed with the project's industry partner, SC Johnson — the product is the partner's; the proof is this city's contribution, and the recommendation it earned now stands in world malaria policy.

Sources:

1. Ochomo EO 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 405 (11 January 2025): 147–156 — the 33.4 percent reduction in first-time infection hazard and 32.1 percent in overall new infections; Achee and Grieco among the authors; funding by Unitaid to the University of Notre Dame; ClinicalTrials.gov NCT04766879.
2. University of Notre Dame, Eck Institute for Global Health and Department of Biological Sciences news (30 September 2025) — the World Health Organization's conditional recommendation for spatial emanators, informed by the AEGIS Kenya study led by Notre Dame; Achee as the project's lead principal investigator and scientific director; Unitaid's "first new class of vector control intervention in decades," carried as Unitaid's words.
3. Newswise / World Health Organization Vector Control Advisory Group report account — the earlier Indonesia trial's reductions of approximately twenty-eight percent (first-time) and forty-one percent (overall) in the reported clusters; the SC Johnson emanator developed with Notre Dame.