Understanding pathways from primary health care to universal health coverage outcomes: a realist review

Introduction Primary Health Care (PHC) rooted in community empowerment, integrated service delivery, and multisectoral action is central to efforts toward Universal Health Coverage (UHC), yet little is known about how PHC reforms influence UHC outcomes across contexts. This review examines how PHC approaches affect population coverage, service coverage, and financial protection by identifying what works, for whom, under what circumstances, and why. Methods A realist review was conducted using studies from countries with the greatest gains in the UHC Service Coverage Index between 2000 and 2021. Forty-two studies met quality criteria following blinded screening, appraisal, and data extraction. Data were synthesized through iterative development of explanatory configurations linking PHC mechanisms, contexts, and UHC outcomes. The evidence base was limited, concentrated mainly in India and China, and largely published after 2020. Results Two key configurations emerged: one on reproductive, maternal, newborn, and child health and nutrition, and another on overall PHC design and delivery. The predominance of RMNCH-focused reforms reflects long-standing reform sequencing in many health systems and highlights how RMNCH platforms often function as foundational entry points for PHC strengthening. Across both configurations, reforms frequently emphasized service expansion, benefit package design, and insurance or financing initiatives, with greater attention to contact than effective coverage. Frontline workers, community organizations, and multisectoral actors played critical roles, while persistent geographic, transport, and equity barriers hindered progress. PHC reforms contributed to improvements in coverage and financial protection but fell short in reaching marginalized groups, reducing financial barriers, and enhancing service quality. Discussion Strengthening community engagement, regulating private sector roles, and advancing multisectoral collaboration remain essential, and further research is needed to understand how PHC strategies function across diverse contexts to better support UHC. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD42024523631 .