Evaluating the effectiveness of insecticide-treated net use in preventing malaria among children under five: a quasi-experimental study

BACKGROUND: Malaria remains a leading cause of morbidity among children under five in Ghana despite widespread deployment of insecticide-treated nets (ITNs). Understanding the effectiveness of ITN use under routine programmatic conditions is essential for guiding national malaria control strategies. This study assessed the impact of ITN use on malaria infection among children under five and explored contextual factors that may influence intervention performance. METHODS: We analyzed nationally representative, georeferenced data from surveys in Ghana. Spatial quantile maps were created to describe regional patterns of ITN ownership, ITN use, indoor residual spraying (IRS), and malaria prevalence. Multilevel regression models, estimated using conventional and Bayesian approaches, examined the association between ITN use and malaria infection while accounting for enumeration area and regional clustering. Inverse probability of treatment weighting (IPTW) based on propensity scores was used to balance covariates, and the marginal odds of ITN use were estimated. We further estimated the risk difference (RD) using a linear probability model. RESULTS: This study included a total of 11,481 children. Sleeping under an ITN led to an estimated 13% reduction in the odds of malaria infection (aOR = 0.87; 95% CI 0.81-0.93) and an absolute risk reduction of 2.2% (RD = - 0.022; 95% CI - 0.037 to - 0.006). Spatial analyses revealed misalignment between intervention coverage and malaria burden, while behavioral and contextual factors likely contributed to the modest effect size. CONCLUSIONS: ITN use provides meaningful but limited protection against malaria infection among young children in Ghana. Strengthening malaria control will require attention to behavioral and contextual drivers of exposure and improved alignment of interventions with local transmission patterns.