Critical Realist Examination of the Mechanisms and Contexts of Successful Primary Care Reforms in Nigeria from 2015 to 2024

Background: Understanding what works, for whom, and under what conditions in primary care reform is essential for evidence-informed policy in Nigeria. This study applies a critical realist framework to examine the mechanisms and contextual conditions associated with successful primary care reform initiatives across Nigeria between 2015 and 2024. Methodology: A realist synthesis combined analysis of policy documents, programme evaluations, and 50 key informant interviews with health system actors across all six geopolitical zones. Realist logic of inquiry structured retroductive reasoning to identify context-mechanism-outcome configurations for each reform programme. Results: Six distinct context-mechanism-outcome configurations were generated. Community ownership emerged as the most consistently generative mechanism across diverse reform contexts. Reforms characterised by co-production with local governments and community health structures demonstrated superior sustainability. Top-down policy mandates without resource alignment consistently failed to activate reform mechanisms. Conclusion: This critical realist analysis provides an original explanatory model of primary care reform success in Nigeria with transferable implications for policy design. Family medicine departments should serve as institutional anchors for co-produced reform initiatives that are contextually grounded and community-endorsed. Keywords: primary care reform, critical realism, context-mechanism-outcome, Nigeria, health policy