Impact of mass distribution on insecticide-treated net coverage and usage in Papua New Guinea

Background Although one of the most operationally challenging malaria control settings in the world, Papua New Guinea (PNG) has distributed over 20 million insecticide-treated nets (ITNs) in the last 15 years. Despite this considerable achievement, malaria cases in PNG are rising. Recent national-level surveys indicate unusually low ITN coverage and usage indicators in some of the highest-burden provinces, raising concerns about the continued effectiveness of this core intervention. Significant knowledge gaps remain around factors impacting ITN effectiveness in PNG, limiting interpretation of the role of ITNs in the context of rising malaria cases. The present study assessed how ITN ownership and usage indicators in three of the highest burden provinces changed after the most recent mass distribution in 2024. Methods This study was conducted in 12 villages across three provinces and collected data on 5671 individuals belonging to 815 households. Surveys were conducted 1–2 months prior, and 5–7 months after programmatic ITN mass distribution. Data were collected through household questionnaires, visual inspection of all ITNs present in households, and matching of ITNs to individual users. Household-level and person-level indicators of ITN ownership and use were evaluated using statistical models. Results Distribution targets were achieved in two provinces but were missed in the third province. Overall, 94.8% of houses owned at least one ITN per person, before, and 99.4% after distribution (p < 0.001). The mean number of ITNs per person rose from 0.55 to 0.64 (p < 0.001), and universal coverage increased from 60.0% before to 69.9% after distribution (p = 0.002). ITN distribution resulted in 61.1% of new ITNs in use and 55.5% of old ITNs lost to follow-up at the post distribution survey. Distribution increased ITN usage evenly across genders and ages and did not change existing overall age- or gender-related usage and sharing patterns. Conclusion Contrasting recent national indicator survey reports, ITN ownership and use are high and sustained by 3-yearly distributions in three PNG provinces accounting for over 40% of malaria cases. Usage predominantly depends on ITN availability but exceeding universal coverage does not further increase usage. Our study demonstrates that post-distribution surveillance is important to confirm the achievement of program targets.