Comparing inductive and deductive methods to understand health service implementation problems: A case study of childhood vaccination barriers

Effective implementation requires a comprehensive understanding of individual, organisational and system determinants. This study aimed to compare inductive and deductive approaches to understand a complex implementation issue. We used childhood vaccination as a case study, an issue with wide-ranging barriers contributing to low vaccine uptake internationally. The study is based on the Behaviour Change Wheel framework, which was derived from several levels of theory: the three components of the COM-B model (capability, opportunity and motivation) can be mapped to the 14 domains of the Theoretical Domains Framework (TDF), which is based on 84 underlying constructs. We rst conducted a review of systematic reviews of parent-level barriers to childhood vaccination. Subsequently we: 1) inductively coded these barriers into a data-driven framework, using thematic analysis; and 2) deductively mapped the barriers to COM-B and TDF domains and constructs. These processes were undertaken by two authors independently, and discrepancies were resolved through discussion. Inductive and deductive results were compared.


Contributions To The Literature
Deductive theoretical approaches to understanding implementation problems, such as the TDF and COM-B, may raise different issues compared to inductive data-driven approaches This paper describes a process for comparing inductive and deductive approaches to understand an implementation challenge of global signi cance We describe a method using several levels of theory, and identify new directions to improve the speci city of theoretical behavioural constructs in future research The paper illustrates how inductive and deductive approaches synergise to produce a more comprehensive understanding of health service barriers than using either approach alone Background Effective implementation of a health service program, guideline or treatment requires understanding a wide range of system, organisational and individual determinants of uptake 1 . This may involve reviewing existing literature for well-established problems, or conducting original research if the issue is new.
Incorporating theoretical models or frameworks can ensure all possible drivers are considered 2 .
The use of theoretical models enables an understanding of the mechanisms of change from individual to system levels, which can then be targeted in interventions. Multiple theories are used in healthcare, from simple models of individual health behaviour change like the Theory of Planned Behaviour 3 , to broader systems thinking approaches to map the complexity of policy drivers 4 . The Behaviour Change Wheel (BCW) is one approach that attempts to bring individual and system level factors together 5 , based on the COM-B (capability, opportunity, motivation -behaviour) model that synthesises 14 behavioural constructs in the Theoretical Domains Framework (TDF) 6 into broader categories.
The TDF summarises the many overlapping constructs in the behaviour change literature, and was developed through expert consensus from 128 theoretical constructs in 33 theoretical models of behaviour 7 . It provides an overview of 14 key theoretical constructs that explain health behaviour, and is a descriptive framework rather than a theory of causality. A separate systematic review of 19 frameworks for behaviour change interventions led to the BCW, which aims to guide the development of interventions by connecting the determinants of behaviour with behaviour change techniques 5 . Developed in conjunction with the BCW, and at its central core, is the COM-B model which proposes that behaviour is a product of the interaction between capability (psychological or physical), opportunity (social or physical) and motivation (automatic or re ective) 5,7 .
The COM-B and TDF have been mapped to each other, but there is some duplication of the current 14 TDF domains across the COM-B components. Table 1 summarises this theoretical relationship.
Primary research is often used to identify barriers to implementation in different health service contexts, and this is the approach generally used with the TDF 7 . Some issues have been well researched, but this evidence must be synthesised in order to inform comprehensive intervention design 8 . Previous reviews have applied theoretical frameworks to help with this. For example, the BCW can be used to describe interventions in terms of broader functions 9 , and the COM-B can be used to display barriers and facilitators at multiple levels (patient, provider, system) 9 . The TDF can be used together with the COM-B to group barriers and facilitators of health outcomes 10 , or as a stand alone framework 11 .
A deductive approach using theory-driven constructs may identify different implementation issues compared to inductive approaches that are data-driven. A deductive application of theory ensures that all psychological constructs relevant to behaviour are considered, even if research has not identi ed every construct. However, since these theoretical frameworks are based heavily on psychological theory, the internal 'motivation' aspect is more clearly de ned than the more external 'opportunity' aspect. This imbalance does not necessarily align with the prevalence and signi cance of practical issues in health service implementation, which might be de ned as "physical opportunity". A hybrid approach can be used to address this 12,13 , but the extra time and expertise required needs to be weighed against the potential bene ts.
The aim of this paper is to compare inductive and deductive approaches to the same implementation issue, and illustrate how these processes can complement each other. We use parent uptake of childhood vaccination as an example of an international issue with wide ranging barriers identi ed in multiple reviews. Beliefs about Consequences: Acceptance of the truth, reality, or validity about outcomes of a behaviour in a given situation Beliefs about Capabilities: Acceptance of the truth, reality, or validity about an ability, talent, or facility that a person can put to constructive use Intentions: A conscious decision to perform a behaviour or a resolve to act in a certain way Goals: Mental representations of outcomes or end states that an individual wants to achieve Motivation: Re ective and Automatic Social/Professional Role and Identity: A coherent set of behaviours and displayed personal qualities of an individual in a social or work setting Optimism: The con dence that things will happen for the best or that desired goals will be attained Motivation: Automatic Reinforcement: Increasing the probability of a response by arranging a dependent relationship, or contingency, between the response and a given stimulus Emotion: A complex reaction pattern, involving experiential, behavioural, and physiological elements, by which the individual attempts to deal with a personally signi cant matter or event Method Theoretical approach The study was based on the BCW framework because it incorporates both individual and system level barriers to behaviour, and is based on several levels of theory: the three components of the COM-B model can be mapped to the 14 domains of the TDF, which is based on 84 underlying constructs 5 .

Context: The Vaccine Barriers Assessment Tool (VBAT project)
This analysis is based on data gathered for the Vaccine Barriers Assessment Tool (VBAT) project, which aims to design and validate a survey tool to diagnose the causes of under-vaccination in children under ve years. Developed in Australia and New Zealand, VBAT aims to incorporate both access and acceptance barriers in a comprehensive tool which will include both short and long form versions, for different uses. An overview of systematic reviews of primary studies on barriers to childhood vaccination was conducted, and 583 descriptions of parental barriers to childhood vaccination uptake were extracted and inductively grouped into categories 14 . Barriers were extracted if they were reported from or relevant to the speci c perspective of parents of children under ve years; barriers from the perspective of health professionals or the health system alone were not included. The ndings of the review were thematically organised into a framework of barriers. In a separate deductive process, the 583 barrier descriptions were mapped to the 14 domain version of the TDF, to check whether any theoretical determinants of childhood vaccine uptake were missing in the systematic review data. The purpose of this exercise for the VBAT project was to ensure that a comprehensive pool of potential survey questions could be generated that captured both access and psychological or acceptance barriers. The inductive review and development of the VBAT items will be reported separately (manuscript in preparation 15 ). In the results of this article, we describe the utility of using both inductive inductive and deductive approaches to identifying drivers of vaccination. Speci c terms are used as outlined in Table 2.
Process Figure 1 illustrates the inductive and deductive processes, supported by regular group meetings with all authors to discuss each step. We used the perspective of parents (not health professionals or health systems), which affected the way the deductive categories were applied.     Emotion Anxiety about vaccination, fear of needles, psychosocial distress *Note: These 4 domains were not included in the rst round of coding. Intentions and goals were later included after discussion with a very lenient interpretation of the inductive barriers to maximise the number of domains covered, given the aim of the exercise was to generate questionnaire items covering all possible behavioural in uences. No inductive barriers could be interpreted as behavioural regulation or optimism.

Discussion
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 con icts 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 con icts at the construct level was more di cult because many constructs within a domain were very similar when applied to the brief barrier descriptions extracted from reviews, for example the in uence of family member opinions could t 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 identi ed 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 speci c 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 identi ed 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 constructs 16 .

Practical implications
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 speci c 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 identi ed in the literature. Secondly, the COM-B model was not speci c 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 speci c 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 undervaccination, 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.

Theoretical implications
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 speci c 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-speci c 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 approach 1 . A third option would be to add more speci c 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 in uence 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 TDF 16

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.

Conclusions
In conclusion, using both inductive and deductive approaches can help achieve a more comprehensive understanding of health service implementation problems; but the TDF approach needs to be re ned in the context of vaccination. The process is subjective so requires a wide range of expertise to reduce biased interpretation and to maximise utility of the identi ed barriers for the speci ed purpose.  VBATpaperAppendix.pdf