Perceived Efficacy and Acceptability of a Spatial Repellent for Malaria Control in Western Kenya: Lessons from a Qualitative Social Science Study Conducted in Conjunction with an Epidemiological Efficacy Trial.

Kenya recorded more than 3 million malaria cases in 2023. Insecticide resistance and changing mosquito behavior have reduced the effectiveness of insecticide-treated nets (ITNs) and indoor residual spraying. Spatial repellents (SRs) show promise for malaria control. The present social science study, which is nested within the Advancing Evidence for Global Implementation of Spatial Repellents clinical trial in Kenya, was conducted to explore SR acceptability and perceived efficacy. Modified trials of improved practices were used to assess participant response to Mosquito Shield™, a transfluthrin-impregnated SR. Structured observations and semi-structured interviews were conducted at 16 intervention and 14 control compounds during five visits over the 24-month clinical trial. The authors remained blinded to study assignment throughout data collection; data were then analyzed by study arm after unblinding. Both intervention and control participants reported reduced mosquito activity inside homes after initial installation. Over time, most intervention participants reported continued efficacy. Controls, who received identical-looking placebo products, reported decreased efficacy. In both arms, participants mentioned discontinuing ITN use. Closely tied to perceived efficacy, acceptability was also influenced by the installation method, the number of units required, the replacement interval, and perceived community opinion. Spatial repellents seem likely to be accepted in this setting when they are perceived as effective and installed satisfactorily. National programs considering SR distribution should anticipate decreased ITN use and emphasize that SRs are meant to complement, not replace, existing interventions. Spatial repellent-related communication should stress proper product use to maximize efficacy. Decreased expenses for products like mosquito coils might incentivize adoption. The present study illustrates the value of social science research parallel to an efficacy trial.