Ivermectin to Control Malaria — A Cluster-Randomized Trial

Abstract

BACKGROUND: Malaria control and elimination is threatened by the spread of insecticide resistance and behavioral adaptation of vectors. Whether mass administration of ivermectin, a broad-spectrum antiparasitic drug that also kills mosquitoes feeding on treated persons, can reduce malaria transmission is unclear. METHODS: We conducted a cluster-randomized trial in Kwale, a county in coastal Kenya in which malaria is highly endemic and coverage and use of insecticide-treated nets are high. Clusters of household areas were randomly assigned in a 1:1 ratio to receive mass administration of ivermectin (400 μg per kilogram of body weight) or albendazole (400 mg, active control) once a month for 3 consecutive months at the beginning of the "short rains" season. Children 5 to 15 years of age were tested for malaria infection monthly for 6 months after the first round of treatment. The two primary outcomes were the cumulative incidence of malaria infection (assessed among children 5 to 15 years of age) and of adverse events (assessed among all eligible participants). Analyses were performed with generalized estimating equations in accordance with the intention-to-treat principle. RESULTS: A total of 84 clusters comprising 28,932 eligible participants underwent randomization. The baseline characteristics of the participants were similar in the trial groups. Six months after the first round of treatment, the incidence of malaria infection was 2.20 per child-year at risk in the ivermectin group and 2.66 per child-year at risk in the albendazole group; the adjusted incidence rate ratio (ivermectin vs. albendazole) was 0.74 (95% confidence interval [CI], 0.58 to 0.95, P = 0.02). The incidence of serious adverse events per 100 treatments did not differ significantly between the trial groups (incidence rate ratio, 0.63; 95% CI, 0.21 to 1.91). CONCLUSIONS: Among children 5 to 15 years of age who were living in an area with high coverage and use of bed nets, ivermectin, administered once a month for 3 consecutive months, resulted in a 26% lower incidence of malaria infection than albendazole. No safety concerns were identified. (Funded by Unitaid; BOHEMIA ClinicalTrials.gov number, NCT04966702; Pan African Clinical Trial Registry number, PACTR202106695877303.).