{ "background": "Access to quality healthcare in rural sub-Saharan Africa remains a critical challenge. While clinic systems are a cornerstone of health policy, rigorous evidence on their causal impact on clinical outcomes is limited, particularly in West African contexts.", "purpose and objectives": "This study aimed to quantify the causal effect of a national rural clinic system on key clinical outcomes in a West African setting, moving beyond descriptive association to robust impact evaluation.", "methodology": "A quasi-experimental difference-in-differences design was employed, leveraging the phased rollout of clinics across districts. We analysed longitudinal patient-level data from national health records. The primary model was specified as $Y{it} = \\beta0 + \\beta1 (\\text{Treatment}{i} \\times \\text{Post}{t}) + \\gammai + \\deltat + \\epsilon{it}$, where $Y{it}$ is the clinical outcome for individual $i$ at time $t$, with district ($\\gammai$) and time ($\\delta_t$) fixed effects. Inference was based on cluster-robust standard errors.", "findings": "Clinic establishment significantly reduced the incidence of severe malaria diagnoses by an estimated 18.2 percentage points (95% CI: 12.7, 23.7). Improvements were also observed in antenatal care attendance and childhood vaccination rates, with effects concentrated in areas furthest from pre-existing urban hospitals.", "conclusion": "The systematic deployment of rural clinics substantively improved population health outcomes, demonstrating their effectiveness as a primary healthcare delivery mechanism in this context.", "recommendations": "Health policy should prioritise sustained investment in rural clinic infrastructure and workforce. Future programmes should incorporate phased implementation to facilitate rigorous monitoring and evaluation.", "key words": "health systems, impact evaluation, difference-in-differences, primary healthcare, sub-Saharan Africa", "contribution statement": "This study provides novel, causally identified evidence on the clinical effectiveness of a nationwide rural clinic network, introducing a robust quasi