The importance of context in implementation research.

This article describes the pertinence of context in HIV/AIDS implementation research. Without attending to context and how it interacts with interventions, national protocols for HIV/AIDS interventions are likely to fail or underperform. With its focus on what works, for whom, under what contextual circumstances, and whether interventions are scalable, implementation research yields context-sensitive designs and enhances the likelihood of scale-up for equitable outcomes. A framework for implementation science is presented alongside a review of published HIV/AIDS protocols for complex interventions. A case study of the South African Prevention of Mother-to-Child Transmission of HIV program highlights the application of complex system improvement principles in developing adaptive and context-sensitive scale-up designs. Preliminary recommendations are provided that can be used to characterize context when reporting interventions and describing how context can be accounted for in implementation strategies.