Dear Editor,

Major public health concerns worldwide derive from emerging societal challenges, such as climate change, population aging, social and health inequities, high burden of non-communicable diseases, poverty, migratory movements (including in the context of humanitarian emergencies), among others. The current context poses challenges in addressing “How to promote health and well-being for all at all ages?,” “How to better prevent disease and minimize its effects through early diagnosis and treatment?,” and “How to tackle adverse social determinants of health and reduce inequalities?” Complex questions demand complex responses, for which there is no single recipe. It has been increasingly advocated that part of these responses lie in capacitating and empowering people for protecting and taking care of their health and creating favorable and supporting environments for evidence-informed health decision-making. In this context, a key ingredient widely acknowledged for addressing current complex public health concerns is health literacy.

Health literacy empowers people to make positive health choices. It refers to the cognitive and social skills that determine the motivation and ability of individuals to access, understand, and use information and that enable them to promote and maintain good health ^1,2. Health literacy implies that people attain a level of knowledge, personal skills, and confidence to make informed decisions about their health and the health of their families, to be active partners in their care, and to effectively navigate health systems ¹. The role of health literacy is even more relevant when it is difficult to distinguish between “useful” and “useless” information. Health information is important; it can generate knowledge for action, but it is not knowledge in itself. Indeed, a major public health concern stems from assuring not only that information is available but that everyone has the capabilities to access, identify, produce, process, disseminate, and use the available information to build and apply knowledge for the health and well-being of themselves and those around them. The difficulties in accessing and using health information intensified with the COVID-19 pandemic. Indeed, the pandemic crisis amplified health disparities within society, disproportionately affecting most vulnerable populations, as those living in poorer socioeconomic conditions and facing difficulties in accessing health services. Therefore, there are still people left behind.

The promotion of health literacy, seen as a determinant of health, is a key priority in the public health policy agenda worldwide. Improving populations’ health literacy levels is linked to several Sustainable Development Goals, being crucial for attaining the social, economic, and environmental ambitions of the 2030 Agenda. But an intricacy is that different people, throughout their lives, may have different needs and resources in health literacy. In this perspective, health literacy has been increasingly seen as a dynamic social practice that develops in a context, is co-produced in social relations, depends on the resources at hand, and, in many cases, is shaped by culture, personal experience, and knowledge. So, ultimately, health literacy intervention that is effective in a certain context is unlikely to produce the same results elsewhere. Also, developing health literacy goes beyond individualistic approaches - it is about creating environments that enable people to obtain, evaluate, and use health information and improve their health literacy skills, as well as fostering key stakeholders (e.g., healthcare providers, service managers, policymakers) to create these environments within the context and demands of people’s daily lives. Additionally, to understand and meet the health literacy needs of the most disadvantaged and socially excluded populations has been a challenge. The fact is that many health programs and strategies including health literacy interventions are generally designed for “Mr.” and “Mrs. Average,” while there is reduced evidence on the specific needs of different segments of communities, which thus tend to be overlooked. This reality implies that we must act to address health challenges that are multidetermined in nature, involving communities to better address their strengths, needs, and preferences in settings that are complex systems. This paradigm calls for a complex intervention approach.

Complex interventions have been defined as interventions with several interacting components, highly flexible and tailored, targeting different groups and aimed at reaching various outcomes ³. Within a “fit-for-purpose” perspective, the intervention context of implementation plays a central role in the intervention’s effectiveness and in its success in reaching all relevant target populations - rather than the traditional “one-size-fits-all” strategy, where a set of technical programs, guidelines, and procedures are applied irrespective of the context. From that standpoint, understanding the dynamic link between context, implementation, and effectiveness is essential to adapt and improve health literacy interventions. Nevertheless, the processes at play in the implementation of an intervention in different contexts are frequently complex and not yet well understood.

Implementation research (IR) is an innovative integrated approach linking research to action, which enables generating evidence to further understand what works, how it works, why, and for whom and supports decision-making on interventions and policy. Indeed, evidence-based practice requires that decisions on interventions and policy be based on the best available, current, valid, and relevant evidence. Specifically, the IR process explores the context in which health literacy interventions are delivered and examines ways in which they may be optimized and barriers may be overcome. It provides critical insights and knowledge concerning acceptability, ability, and willingness to adhere to health literacy programs and actions, as well as factors of adherence/participation. IR helps define the content and implementation strategy of the health literacy intervention, ensuring that it takes proper account of communities and setting characteristics and that its outputs are built in situ and are needed and wanted by all the stakeholders involved in the implementation.

The work of the NOVA National School of Public Health (NOVA NSPH) in the development of the scientific area of health literacy and IR has been ongoing over the years. The NOVA NSPH is currently coordinating a set of IR projects aimed to produce evidence on health literacy needs and resources, especially among most vulnerable populations, and to support the co-creation and implementation of innovative health literacy interventions with social and health impact by engaging stakeholders and communities and integrating their experiences and social practices ⁴. Additionally, NOVA NSPH projects have been dedicated to monitoring and evaluation of the implementation processes and outcomes of such complex interventions. Overall, these efforts are intended to contribute to the underpinnings of health literacy promotion research, practice, and policy.