Iterative Multidisciplinary Development and Evaluation of a Patient-Facing Social Determinants of Health Chatbot Using Synthetic Data Simulation: Mixed Methods Study.

Experimental huts are the gold standard for assessing vector control tools including insecticide-treated net (ITN), indoor residual spray (IRS) and spatial emanator (SE) products under semi-field conditions that simulate real-world settings. They provide a robust method for evaluating the bioefficacy of vector control products while reducing the need for cluster randomised controlled trials of each new product within a product class [–]. Experimental huts are routinely used in non-inferiority trials to demonstrate that a new product is similarly effective against mosquitoes as a first-in-class product with established clinical efficacy [] within a predetermined non-inferiority margin [, ]. Originally developed in the 1940s and used to evaluate the efficacy of IRS products [] during the Global Malaria Eradication Program [], experimental huts are now considered the gold-standard approach for assessing the bioefficacy of ITNs, IRS and SE products as part of dossiers used for World Health Organisation (WHO) prequalification [, ], a prerequisite for procurement by the United Nation agencies for deployment in malaria endemic regions []. The design of experimental huts has been standardised to control factors such as internal volume, mosquito entry and exit points, and the absence of furniture. Huts are designed so that mosquitoes that enter are retained and can be more easily recaptured than in local village homes. Ant control methods are incorporated to minimise mosquito predation and loss from scavenging ants. Experimental hut trials are designed to measure key entomological endpoints, primarily mosquito mortality, as well as blood-feeding, deterrence, and induced exophily [, ]. However, there are several experimental hut designs currently in use which differ in size and in the area and position of mosquito entry and exit points []. Evidence suggests that these structural variations can influence mosquito behaviour and, consequently, the efficacy outcomes measured [, ]. However, the use of different hut types across geographical regions in sub-Saharan Africa, with heterogeneous vector bionomics and insecticide-resistance levels complicates the interpretation of trial data, and it is unclear whether observed differences in the outcomes of different trials reflect true vector population differences or are to some degree an effect of hut design. To address this gap in our knowledge, we conducted a comparative evaluation of four experimental hut designs in one site in Tanzania using pyrethroid and chlorfenapyr–pyrethroid ITNs and benchmarked the findings against a contemporaneous sister trial conducted in West Africa []. The study aimed to (1) assess how each hut type affects key entomological endpoints and (2) determine whether each hut design produces consistent estimates of the relative efficacy of a second-in-class chlorfenapyr–pyrethroid ITN compared with the first-in-class product, using a predefined non-inferiority margin of 7%.