Background: Malaria in eastern Indonesia remains high despite significant reductions and local elimination in other parts of the country. Malaria control activities that have been implemented include early diagnosis and prompt treatment, provision of Long-lasting insecticide-treated nets (LLINs), and indoor residual spraying (IRS). To expedite malaria elimination in this region, a rapid entomological assessment combined with human behaviour observations (HBOs) were conducted in eight high malaria endemic regencies in Papua Province, Indonesia. The present study focuses on identifying gaps in protection against mosquito biting indoors and outdoors that may contribute to the sustained transmission and persistently high endemicity. Methods: This study was conducted alongside a rapid entomologic assessment, including human landing catches (HLCs) of adult mosquitoes. Human behavior was documented by direct observations during HLCs. HBO data focused on temporal (over the night) and spatial (domestic or peri-domestic) presence, alongside bed net usage and sleeping patterns. Household questionnaires, also conducted during entomological collections, documented data on house structure materials, practices against mosquito bites, livestock presence, as well as intervention usage. Results: Analysis of human behaviors in each regency identified several indoor and outdoor gaps in protection against mosquito biting. Human exposure to mosquito bites was driven by ITN usage, IRS coverage, indoor presence without protection prior to sleeping, absence of mosquito house screens, and outdoor presence without protection. Conclusions: Data demonstrates multiple gaps in protection against mosquito exposure in all eight regencies of Papua evaluated. Indoor interventions require optimization, while current vector control activities do not presently address outdoor exposure. Measured spatial and temporal exposure may be utilized to understand protective vector interventions that may function in these spaces while also pointing to continued exposure. Additional interventions, such as community-based larval source management, may reduce exposure overall, while novel interventions like spatial repellents may fill some gaps in protection – alongside optimized case detection and treatment. Results suggest that the present strategy may be insufficient to eliminate malaria in the region, and a rethought evidence-based and adaptive strategy is required.

The authors have declared no competing interest.

The study was supported by the United Nations International Children's Emergency Fund (UNICEF) and the government of Indonesia National Research and Innovation Agency (BRIN), Republic of Indonesia, through funding from Health Research Organizations

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the Ethics Committee of Research in Health, Medical Faculty of Hasanuddin University, Makassar, Indonesia No: 281/UN4.6.4.5.31/PP36/2019 and (29 January 2021) No: 40/UN4.6.4.5.31/PP36/2021

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All datasets generated and analyzed during this study are included in the manuscript