Adaptation of evidence-based interventions upon implementation into new practice settings is universal, yet poorly understood. During a cross-site evaluation of the implementation of a proven intervention for pediatric asthma care coordination into 4 resource-challenged settings, we conducted in-depth interviews with site representatives, who reported how and why they modified intervention components. Interview notes were coded for themes. We focused on a single theme from a respondent who described the adaptation process as "backing" the intervention into ongoing services; we found evidence of a similar process at other sites. We labeled this process "retrofitting" to signify adaptation that consists of altering existing services to align with intervention components, rather than modifying the intervention to fit a new setting. Advantages of retrofitting may include allowing organizations to keep what works, capitalizing on existing support for program activities, elevating the role of local knowledge, and potentially promoting the sustainability of effective innovations.

The Merck Childhood Asthma Network (MCAN) initiative selected five sites (New York City, Puerto Rico, Chicago, Los Angeles, and Philadelphia) to engage in translational research to adapt evidence-based interventions (EBIs) to improve childhood asthma outcomes. The authors summarize the sites' experience by describing criteria defining the fidelity of translation, community contextual factors serving as barriers or enablers to fidelity, types of adaptation conducted, and strategies used to balance contextual factors and fidelity in developing a "best fit" for EBIs in the community. A conceptual model captures important structural and process-related factors and helps frame lessons learned. Site implementers and intervention developers reached consensus on qualitative rankings of the levels of fidelity of implementation for each of the EBI core components: low fidelity, adaptation (major vs. minor), or high fidelity. MCAN sites were successful in adapting core EBI components based on their understanding of structural and other contextual barriers and enhancers in their communities. Although the sites varied regarding both the EBI components they implemented and their respective levels of fidelity, all sites observed improvement in asthma outcomes. Our collective experiences of adapting and implementing asthma EBIs highlight many of the factors affecting translation of evidenced-based approaches to chronic disease management in real community settings.