• Jue Tao Lim, Diyar Mailepessov, Chee-Seng Chong, Borame Dickens, Yee Ling Lai, Youming Ng, Lu Deng, Caleb Lee, Li Yun Tan, Grace Chain, Soon Hoe Ho, Chia-Chen Chang, Pei Ma, Somya Bansal, Vernon Lee, Shuzhen Sim, Cheong Huat Tan, and Lee Ching Ng.
• Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
• J Travel Med. 2024 Aug 6.

BackgroundMatings between male Aedes aegypti mosquitoes infected with wAlbB strain of Wolbachia and wildtype females yield non-viable eggs. We evaluated the efficacy of releasing wAlbB-infected Ae. aegypti male mosquitoes to suppress dengue.MethodsWe specified the protocol of a two-arm cluster-randomized test-negative controlled trial (cRCT) and emulated it using a nationally representative test-negative/positive database of individuals reporting for febrile illness to any public hospital, general practitioner or polyclinic. We retrospectively built a cohort of individuals who reside in Wolbachia locations versus a comparator control group who do not reside in Wolbachia locations, using a nationally representative database of all individuals whom report for febrile illness and were tested for dengue at the Environmental Health Institute/hospital laboratories/commercial diagnostic laboratories, through general practitioner clinic, polyclinic or public/private hospital from EW1 2019-EW 262022. We emulated a constrained randomization protocol used in cRCTs to balance dengue risk between intervention and control arms in the pre-intervention period. We used the inverse-probability weighting approach to further balance the intervention and control groups using a battery of algorithmically selected sociodemographic, environmental and anthropogenic variables. Intention-to-treat analyses was conducted to estimate the risk reduction of dengue given Wolbachia exposure.ResultsIntention-to-treat analyses revealed that, compared with controls, Wolbachia releases for 3, 6, 12 or more months was associated to 47%(95%CI:25-69%), 44%(33-77%) and 61%(38-78%) protective efficacy against dengue, respectively. When exposed to 12 or more months of Wolbachia releases, protective efficacies ranged from 49%(13-72%) to 77%(60-94%) across years. The proportion of virologically confirmed dengue cases was lower overall in the intervention arm. Protective efficacies were found across all years, age and sex subgroups, with higher durations of Wolbachia exposure associated to greater risk reductions of dengue.ConclusionResults demonstrated that Wolbachia-mediated sterility can strengthen dengue control in tropical cities, where dengue burden is the greatest.© The Author(s) 2024. Published by Oxford University Press on behalf of International Society of Travel Medicine.

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