From laboratory to field: Progress and prospects of the phase conditional approach in two decades of sterile insect technique research against Aedes aegypti in Indonesia.

Dengue remains a major public health concern in Indonesia, and despite recent progress in vaccine development, vector control remains essential to limit dengue outbreaks and occurrence of clinical cases. Among emerging approaches, the radiation-based sterile insect technique (SIT) has gained attention as an environmentally friendly vector control strategy. This review synthesizes two decades (2004-2024) of SIT research and development against Aedes aegypti in Indonesia, tracing the programme's evolution from unstructured pilot releases to a structured phased conditional approach (PCA) framework that culminated in a recent small-scale field trial in Bandung city. Taking the field trial as the central case study, we identify a core challenge: while SIT can significantly reduce vector populations, suppression remains incomplete and impermanent without optimized integration, as evidenced by post-release population rebound. Further synthesized challenges include navigating the impact of geographical genetic diversity on mating competitiveness, ensuring long-term programme sustainability through stakeholder commitment, and cost-effectiveness concerns for resource-limited settings. To guide the transition toward the pre-operational Phase 3, we propose a dedicated, prioritized research agenda including cluster-randomized controlled trials with entomological and epidemiological endpoints, factorial designs to isolate intervention effects, and development of genetic sexing strains and tailored release protocols, to improve cost-efficiency and prevent population rebound. This synthesis provides a programmatic framework for interpreting Indonesia's SIT development and may inform other dengue-endemic countries considering SIT integration into vector-control programmes.