Advancing the science of intervention scale-up is essential to increasing the impact of effective interventions at the regional and national levels. In contrast with work in high-income countries (HICs), where scale-up research has been limited, researchers in low- and middle-income countries (LMICs) have conducted numerous studies on the regional and national scale-up of interventions. In this article, we review the state of the science on intervention scale-up in both HICs and LMICs. We provide an introduction to the elements of scale-up followed by a description of the scale-up process, with an illustrative case study from our own research. We then present findings from a scoping review comparing scale-up studies in LMIC and HIC settings. We conclude with lessons learned and recommendations for improving scale-up research.
Keywords: implementation science; intermediary organizations; scale-up; scaling up.