In October 2023, the third edition of the impactful book “Dissemination and Implementation Research in Health: Translating Science to Practice” was published (1). The book effectively points toward the advancements and knowledge gaps in the field of research. Knowledge development and support for implementation research and practice are desirable and necessary. Implementation science is a rapidly developing research field with immense potential to improve the implementation of public health policies, programs, and practices, thereby having an impact on population health. However, a key task that needs to be performed in public health and implementation science is to address and promote health equity (2, 3). With growing health inequities in many communities and societies, it is crucial to focus explicitly on health equity when implementing and putting public health actions into practice. In this context, it should also be underlined that public health practitioners are implementing and scaling “things” (i.e., public health actions) whether they are using implementation science or not, and the number of public health practitioners far outweighs the number of implementation researchers. Viewed positively, this means potential for improved population health impact and increased health equity if the implementation competence is strengthened among public health practitioners.

At the same time, there are worrying signs of a “second implementation gap,” and these signs are not explicitly addressed in the Brownson et al. (1) book. This gap refers to the recreation of the research-practice gap, a challenge that implementation research was originally intended for and should help to overcome. As implementation science has matured, various researchers have contributed to thoughtful self-reflection (4, 5), including those highlighting the “second implementation gap” (6–9). In this article, I continue this path and make a specific call to public health researchers and practitioners to be aware of the “second implementation gap” and suggest actions for handling the gap in public health.

Simply put, implementation means introducing new ideas into an organization, usually to try new methods, practices, technologies, systems, or policies (10). Implementation science involves research on processes and outcomes when research-based knowledge and evidence are introduced and used in different settings (11). Thus, implementation research aims to bridge the much-discussed “gap” between research and practice. Implementation is often demanding, and failure is common when introducing new methods and practices. For example, a decision to implement a new school-based method taken by upper-level school management involves teachers and school health professionals at lower organizational levels doing new “things,” but often without the resources to manage the new method. Given the risk of failing, implementation research is sometimes referred to as “misery research.”

It is common to say that it takes an average of 17 years for research to become routine in health care practice (12). While the time estimate is debatable, the implementation research goal is to help practitioners, managers, policymakers, and researchers anticipate common barriers and troubleshoot strategies for successful implementation. Finding solutions is crucial to shorten the time for uptake of research and evidence and for integration in practice and policy in public health and other health-related areas.

Recently, a “new” research-practice gap seems to have emerged in implementation research and practice despite commendable attempts to simplify the sometimes inaccessible and jargon-ridden implementation literature for practitioners (13). The research community discusses this problem as a “second implementation gap” or a “paradox” referring to a recreation of the research-practice gap (6–9). It is easy to see the irony in that research intended to bridge the research-practice gap has come to distance itself from the practice it is meant to improve. The fact that there currently are up to 200 theoretical models and frameworks to guide, analyze, and evaluate implementation in the health field effectively illustrates the problem. While some models and frameworks are used frequently, such as the Consolidated Framework for Implementation Research [CFIR, (14)], the Quality Implementation Framework [QIF, (15)], and the Reach-Effectiveness-Adoption-Implementation-Maintenance (RE-AIM) framework (16, 17), others have limited use (18). Also, few of these models and frameworks are known, used and fully relevant for public health practitioners (19). That said, it should be noted that theoretical and applied implementation researchers and public health practitioners are at different places on the translational spectrum (5). It means that researchers might find themselves on the basic science research to translation to practice and communities' spectrum, whereas public health practitioners usually are working on the translation to practice and community spectrum. Fortunately, implementation researchers have highlighted the problem of growing distance to the real-world practice where the research is to be used and have proposed both research agendas based on practitioners' perspectives (20) and ways for researchers and practitioners to come together.

Inspired by Lyon and colleagues (7), I propose four bridging actions to increase collaboration between researchers and practitioners, with a focus on implementation in public health:

Researchers and public health practitioners need to work together to bridge both the “first” and “second implementation gap” in public health. For this to happen, managerial and political support is needed. Ultimately, improved researcher-practitioner collaboration aims to ensure that evidence-based public health programs, practices, and policies are implemented as effectively as possible and can contribute to good and equitable health for the entire population. As we know, public health interventions work more effectively in more favored groups in society (e.g., high socioeconomic status groups), and effective public health implementation also risks increasing existing health inequities rather than reducing them. Therefore, improved knowledge and rapprochement between implementation research and public health practice are crucial to address health equity and societal challenges and to contribute to developing healthy and sustainable societies.

RL: Conceptualization, Writing – original draft, Writing – review & editing.