The UI-FHS project worked at the sub-national level in Ethiopia to implement the Reaching Every District using Quality Improvement (RED-QI) approach across more than 2,700 health facilities in 103 woredas across 6 regions. The aim of the RED-QI approach is to strengthen the capacity of health workers to address challenges in immunization service delivery by using quality improvement tools to reach the most underserved areas. This report describes the findings to an inquiry that aimed to identify what features of the RED-QI had been sustained and what factors are needed to ensure its sustainability.