Perspectives in the Development of Tools to Assess Vaccine Literacy

"A better understanding of the causal relationship between VL [vaccine literacy] and vaccination will provide a better basis for communication and health education campaigns."



Vaccine literacy (VL) is the ability to find, understand, and evaluate vaccination-related information to make appropriate decisions about immunisation. Various instruments have been developed to assess VL, although they are limited by the number and complexity of influencing factors. The objective of this study is to suggest a framework for developing new tools for a more extensive assessment of VL. It updates earlier literature reviews on VL and related tools, explores its relationship with vaccine hesitancy (VH), and examines associated variables like beliefs, attitudes, and behaviours towards immunisation.



The methodology involved:

1. Updating the researchers' earlier scoping review, published in 2023;
2. Performing a post-hoc analysis of data from a survey conducted in mid-2020 through mediation and factor analysis; and
3. Developing a theoretical framework based on the existing literature, a backward citation search, and the post-hoc analysis.

The 17 selected papers included diverse populations, with sample sizes ranged from 133 to 12,586 individuals. Participants were mostly young female adults. Nine publications out of the 17 confirmed the association between VL and attitudes, vaccine acceptance, or intention to be vaccinated, while three showed an indirect, mediated effect.



The scales employed in the studies were mainly modified versions of the HLVa-IT tool, which aims at measuring VL levels associated with routine vaccination in adulthood. It consists of five questions assessing functional VL (FUVL), in addition to five and four items for interactive and critical skills, respectively. A similar construct measure has also been used in parents of children. Based on the same construct, a measure was also developed and largely used to assess specifically COVID-19 VL (COVID-19-VLS). In this tool, the interactive and critical subscales have been merged and identified as interactive-critical VL (ICVL).



The post-hoc analysis of the 2020 survey data (N = 885) showed a significant mediating effect of ICVL between the independent variable "education" and each of the "3Cs" (accounting for 32%, 25%, and 57% of the total effect for confidence, complacency, and convenience, respectively). The only significant indirect effect of FUVL was between education and confidence, accounting for only for 11% of the total effect.



Reflecting on the role of VL toward VH as illuminated through the current review, the researchers note: "Since published studies are cross-sectional online surveys with a one-time measurement of VL levels, it is difficult to infer precise causalities. Furthermore, their heterogeneity prevents comparisons in terms of methods used, results, and variables that may have influenced interpretation. For all these reasons, understanding the impact of VL remains challenging, although current literature is substantially more in favor of a relationship between higher VL levels and vaccine intention, acceptance, or uptake. Nonetheless, these findings allow considerations on the association of VL with other variables, its mediating role, and prospects for future research."



Following the above steps, a theoretical framework (see above) was developed that depicts the relationship between knowledge, motivation, and competencies, incorporating them along with functional, interactive, and critical VL levels. Moderators (proximal and distal determinants) and possible mediators (i.e., variables that explain the reasons and mechanisms behind outcomes) were included as well. These variables include communication, knowledge, beliefs, attitudes, behaviours, self-efficacy, and competencies. The positioning of VL in the framework at the intersection between sociodemographic antecedents and attitudes, leading to behaviours and outcomes, explains why and how VL can directly or indirectly influence vaccination decisions by countering VH and operating at personal, as well as at organisational and community levels.



Based on this theoretical framework, the researchers discuss:

• Current VL tools: Performance-based tools appear more suitable for estimating individuals' skills in the health care domain, while self-reported measures are better for assessing individuals' attitudes and knowledge beyond reading and numeracy, such as understanding the value of vaccination. Considering the domains relevant to VL (disease prevention and health promotion), the use of subjective VL tools, like the HLS19-VAC Instrument for measuring vaccination literacy, seem appropriate for that scope.
• Future VL tools: Vaccination is a primary prevention practice, mainly aimed at healthy people, which may also require an assumption of responsibility and decisions on behalf of others. Thus, the skills needed to navigate, understand, evaluate, and apply information related to immunisation are likely to differ from those needed for other health issues. These aspects must be taken into account in the development of new tools. Based on the theoretical framework, the researchers outline potential new VL tools:
  • Motivation: It is possible to design VL tools to assess motivation by adapting items from the Protection Motivation Theory, which explains how people respond to fear-evoking or threatening messages, or from the Health Belief Model, which explains and predicts health behaviours by examining attitudes and beliefs.
  • Knowledge: Evaluating the level of crystallised knowledge through a vaccine quiz can offer a straightforward, relevant, and efficient performance-based method. Items can be selected from vaccine scales available in the literature, as well as online resources provided by academic and international institutions. Common questions on the knowledge of vaccines and diseases should be identified and used for comparability purposes, while taking into account cultural and socio-economic differences between populations.
  • Competencies: Competencies can be viewed as a set of knowledge, skills, capabilities (abilities), and behaviours that contribute to the individual's performance. Given that knowledge on vaccines can be evaluated as described above, and that skills and abilities can be assessed through the existing VL scales (such as the interactive and critical sub-scales of HLVa), it is suggested to complete the assessment of competencies by incorporating standardised items that evaluate intention to be vaccinated (intended as precursor of behaviour), together with the educational level of respondents.
  • Composite tools: Using similar metrics on all elements studied, balancing them at the same time and considering their association with each other, a composite-possibly unit-weighted VL score can be sought for future assessments. In addition to separately measuring each scale included in a multidimensional framework, adding a standardised combined index would allow a simplified representation and easier interpretation of results, as well as improving statistical power.
  • Specific VL measures and selected populations: Questions included in new VL tools should be adapted to the specific context for which the measure will be intended.

"Such measures will ease further research about the direct and the mediating role of VL towards outcomes and its relationship with VH, as well as on unexplored aspects, such as the longitudinal evolution of VL in different populations and contexts, and the application of research in organizational literacy. Furthermore, the assessment of VL across various categories of populations and patients, in addition to healthcare workers, can also be the target of new tools."