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Replicating Evidence-Based Prevention Interventions and Policies: Why is fidelity important?

Before we talk about replicating evidence-based (EB) interventions with fidelity, let’s look at heart surgery. In 1953, Dr. Michael DeBakey performed the first successful carotid endarterectomy, which involved removing the plaque in the carotid artery, a procedure which would end up saving millions of lives up into the 21st century. This technique thus became ‘evidence-based’ and was applied in practice; and cardiovascular surgeons around the world have been trained to follow his procedures as he designed them. But we could imagine what would happen if some surgeons decided to do something different, not following protocol, and their patients sickened or died. Would we question the DeBakey method or would we blame the failed surgery on not following protocol?

Let’s now look at our own EB prevention practices. We have EB prevention interventions and policies that have been studied in rigorous research to consistently achieve positive outcomes. These interventions are based on theories on human development and behavior and use learning techniques appropriate for the target group. If there is any alteration of these key elements, the intervention is not only different, but could be ineffective and even harmful.

But prevention professionals are often faced with the need to adapt the intervention to better fit the population of their community, in regard to such issues as language, setting, or cultural depictions. There is guidance to do so responsibly and without losing the fidelity to the core features that must be retained, for example, age of the target group, appropriate delivery methods, and specific amount of exposure to the material. Several sources are helpful in this process including the U.S. Substance Abuse and Mental Health Administration and the work of Felipe Castro and his colleagues from Arizona State University. That guidance is summarized below. Key to both of these references is that responsible changes can be made to adapt an intervention to a specific group. But, like the DeBakey method, the essential ‘working parts’ of the intervention--its content, structure, and delivery strategy--MUST remain as these were found to be the effective elements which produced the successful outcomes.

See this chart from the work of Castro and colleagues where they analyze an intervention to determine how it would match or not with their “New Target Group.” What is important are the potential “Consequences” of these ‘mismatches’. Altering any of these foundational components will change the intervention and could potentially cause harm.

So, for instance, an obvious challenge is changing the language for a new target group. If the target population speaks primarily Hindi, offering the intervention in the original English will not be understood. However, a cautionary note, straight translation from the original language of the intervention into the language of the new target group has to be done carefully so the meaning of the concepts of the words are not lost. If translations are made they should be done by those familiar to prevention concepts and back-translation should be made to assure accuracy. Similarly, if the intervention was initially tested in a predominantly white, middle class population in the United States or Europe, adaptations to other cultures (with different values, beliefs, and/or norms) must be made without losing the foundational features of the EB intervention.

Perhaps not so obvious is the level of vulnerability or risk in the new target population. If the original EB intervention was designed for a low-risk or universal risk population, it may not have strong outcomes if delivered to a more vulnerable or higher risk population.

Guidance for adaptation:

1. First of all is the selection of an evidence-based intervention or interventions to address the needs of the target group. For this we refer you to the Nugget: Planning for the Implementation of Evidence-Based Prevention Interventions and Policies.

2. Once you and your community identify the needs of the target population and an intervention or interventions are selected, a review of the special characteristics of the intended participants of the intervention (for example: age, gender, ‘risk status’ such as initiated substance use or other problem behavior; cultural issues) content, structure, and delivery style should be reviewed in order to fully understand the intent and ‘map’ of the intervention. Oftentimes a logic model of the intervention is available. The model should not only be reviewed by you and your team (that should include key stakeholders) but focus groups with representatives of the target population should be conducted by experts with focus group training.

3. Through the input of the focus groups and your team, identify areas where adaptations need to be made without altering the content, structure or delivery style of the intervention.

4. Conduct a pilot of the intervention modified ONLY as to language and images. In the pilot collect data on short-term outcomes (e.g., knowledge, attitudes, normative beliefs, skills) AND conduct focus groups using expert focus group facilitators.

5. Review the outcomes of the pilot. List areas for potential adaptation.

Here are some pointers from the U.S. Substance Abuse and Mental Health Services Administration about adapting a program for a new community that are very useful:

Change capacity before changing the program. It may be easier to change the program but changing local capacity to deliver it as it was designed is a safer choice.

Consult with the program developer. Consult with the program developer to determine what experience and/or advice he or she has about adapting the program to a particular setting or circumstance.

Retain core components. There is a greater likelihood of effectiveness when a program retains the core component(s) of the original intervention.

Be consistent with evidence-based principles. There is a greater likelihood of success if an adaptation does not violate an established evidence-based prevention principle.

Add, rather than subtract. It is safer to add to a program than to modify or subtract from it.

As important as these guidelines are for prevention practitioners; perhaps they are even more important to prevention researchers and evaluators, who want to assess the impact of evidence-based interventions and policies adapted for new populations. Again, in these situations, it is important to maintain the fidelity to the design of the intervention—i.e., the same targets (age, gender, level of vulnerability), content, and structure of the intervention--as these are grounded on theories of human development and behavior change--and delivery strategy as this relates the age-appropriate learning theories. Fidelity to these foundational elements provides the best opportunity for successful outcomes.


Castro, FG, Barrera, Jr. M., and Martinez, Jr., CR. (2004). The cultural adaptation of prevention interventions: Resolving tensions between fidelity and fit. Prevention Science, 5: 41-45.

Castro FG, Yasui M. Advances in EBI Development for Diverse Populations: Towards a Science of Intervention Adaptation. Prev Sci. 2017 Aug;18(6):623-629.

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