Overall, we found it useful to synthesise health service implementation barriers using both inductive and deductive methods to gain a comprehensive understanding of the barriers to childhood vaccination. The inductive data-driven categories represented the primary research data in a clearer way than the deductive theoretical domains, with better differentiation; but the four missing theoretical domains were useful as a way to identify key gaps to be addressed in the item pool for developing a new tool to diagnose the causes of childhood under-vaccination.
Resolving conflicts at the domain level was relatively straighforward, with 100% agreement reached quickly for the most relevant domain. However there were some barriers that could have been placed in 2 or 3 domains. For example, previous experience of vaccine side effects could be framed as knowledge, beliefs or salient events. Resolving conflicts at the construct level was more difficult because many constructs within a domain were very similar when applied to the brief barrier descriptions extracted from reviews, for example the influence of family member opinions could fit within group identity, social norm or social pressure. The decisions made at construct level were arguably more subjective than the domain level, but both needed to be considered to make sense of many barriers that could be framed in different ways.
For this study it was necessary to go into more theoretical detail than the commonly used models: the COM-B and TDF. Importantly, the gaps identified in our inductive review would not have been found if the analysis had only been done at the COM-B level, as all six components were addressed by the 10 inductive domains. In addition, the 14 TDF domains were still not specific enough for two coders to reliably map the barrier data so we were required to go back a step to the 84 theoretical constructs that informed the TDF development. We found it helpful to use a combination of domain and construct level to map the data. A previous review using the TDF identified some issues that could not be mapped to the TDF, including clinician and patient characteristics. However, some of these could be mapped at the construct level depending on the framing, such as under professional identity, skills, environment x person and resources constructs16.
This paper provides a methodology for anyone seeking to understand an implementation issue that already has a large amount of qualitative and/or quantitative research – complementing an earlier paper that focuses on how to apply the TDF in primary qualitative research 7. There are several practical implications for other researchers seeking to comprehensively understand implementation barriers using theoretical models in this way. Firstly, researchers need to decide on very specific framing for a health situation. In our case we decided we would only consider the parent perspective on vaccinating their child, which determined how we framed barriers relating to the doctors’ knowledge. Conducting this process from the health professional perspective would produce different results in terms of the theoretical constructs identified in the literature. Secondly, the COM-B model was not specific enough with uneven explanation of different barrier types; so researchers may need to go into more detail at domain and construct level to interpret the data. Thirdly, theory was useful for identifying gaps in an inductive review of literature, but inductive categories made more sense for the specific implementation topic. The value of using a deductive theory-driven approach may depend on available resources, given this process took 2 authors with prior knowledge of behavioural models around 2 weeks for coding and discussion. For our purposes, this review will inform the development of a diagnostic tool to measure the causes of under-vaccination, requiring us to include the widest possible range of behavioural drivers. For other projects, it may be more prudent to focus only on the theoretical drivers that are within an organisation’s control to address, or to identify inductive issues from the perspective of key stakeholders to ensure their interest and support.
More generally, this study has implications for theoretical models commonly used in implementation science. Some constructs are vague and became catch alls, such as barriers and facilitators. Others are too specific and hard to distinguish, particularly group vs social norms, which could be combined into one TDF domain. In our experience, the decision was often between constructs in different domains, rather than constructs within a domain, suggesting that there are some issues with the way the TDF domains are differentiated. On the other hand, the construct level was often too subjective and detailed to identify clear gaps in data. This suggests that overarching models like the COM-B and TDF need to be supplemented with more context-specific models for different health areas (e.g. prevention versus treatment of infectious disease), targets of behaviour change (e.g. parents versus doctors), and the context (e.g. higher resource settings where psychological barriers may be more important, versus lower resource settings where practical access issues require greater differentiation). Another option would be to use broad implementation frameworks that include practical issues like cost, such as the Consolidated Framework for Implementation Research (CFIR)17. Other researchers have found it helpful to combine the TDF and CFIR for a more comprehensive approach1. A third option would be to add more specific domains to the next version of the TDF to better differentiate between issues relating to “Environmental Context and Resources”. In our review, this covered a very wide range of issues: socio-economic issues such as having low income, societal issues like the influence of media, health system issues like vaccine supply and cost, and individual access issues like distance and time. This was found to be a catch all category in many previous reviews of clinicians and patients using the TDF16,18−22, so is not limited to the issue of vaccination barriers. For example, a review of barriers to low back pain guidelines found this domain was common to 4/5 clinician behaviours while many other domains were not covered at all20. Another review on diabetic screening identified 17 barriers in this domain versus 6 for the next most common domain18. Further development of this construct may need to be specific to different health topics.
Strengths and limitations
This study addressed reliability by using a method of independent coding using both inductive and deductive approaches. Our team included a wide variety of expertise to help contextual framing for theoretical constructs as applied to inductive barriers. The limitations include restricting our review data to parent barriers only, which affected the way that health professionals’ and heatlh system barriers were conceptualised. We also applied only one overarching framework to behaviour change models, and acknowledge that there are many other approaches to this theoretical issue.