What is the WHO recommended phased testing pathway for genetically modified mosquitoes?
The recommended pathway involves four phases.
- Phase 1 involves initial studies on safety and efficacy, conducted in the laboratory and in cages that contain a small number of mosquitoes. All of these studies are conducted indoors under appropriate containment to prevent escape of the modified mosquitoes into the environment. If the modified mosquitoes demonstrate the desired biological and functional characteristics, testing may move forward.
- Phase 2 expands contained testing under conditions of physical or ecological confinement, intended to limit outward migration of the modified mosquitoes by studying them in large outdoor cages or under geographic/spatial/climatic isolation. This will examine whether the modified mosquitoes continue to show expected characteristics that predict an ability to reduce disease transmission. Depending on Phase 2 results, testing may proceed to Phase 3 of revert to conduct additional studies.
- Phase 3 includes open release trials to assess performance under various disease transmission conditions. In this phase, the ability of the modified mosquitoes to reduce the incidence or prevalence of infection or disease can be directly measured. If Phase 3 testing demonstrates sufficient efficacy and safety, regulators and policy makers may consider wider implementation of the product as a public health tool.
- Phase 4 entails ongoing monitoring of the product’s effectiveness and safety under operational conditions.
Phases 1 through 3 may need to be repeated to improve the technology and refine the procedures until the requirements for moving to the next phase are met. If the genetic modification is a self-sustaining gene drive that is expected to persist in the environment, the phased testing pathway may be more realistically conceived as a continuum of expanding releases.
Decisions to move forward from one testing phase to the next will require appropriate regulatory authorization and the agreement of the communities hosting the trials.
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