Measuring Vaccine Hesitancy: The Development of a Survey Tool

"Publics are changing, embracing their rights to information, and their rights to choice. A certain amount of questioning by new parents, or parents faced with new vaccines or combinations of vaccines, would be considered responsible. Keeping an open dialogue is fundamental to building trust. These survey tools are primarily aimed to better understand the public concerns and thereby better respond to the issues that are relevant to them."

As explained in this paper, in March 2012, the Strategic Advisory Group of Experts on Immunization (SAGE) Working Group on Vaccine Hesitancy (WG) was convened to define the term "vaccine hesitancy" (a delay in acceptance or refusal of vaccination despite availability of vaccination services), as well as to map the determinants of vaccine hesitancy and develop tools to measure and address the nature and scale of hesitancy. The WG developed a matrix of the determinants of vaccine hesitancy informed by a systematic review of peer-reviewed and grey literature, as well as by the expertise of the WG. The matrix mapped the key factors influencing the decision to accept, delay, or reject some or all vaccines under three categories: contextual, individual and group, and vaccine-specific. These categories framed the menu of survey questions presented in this paper to help diagnose and address vaccine hesitancy.

These survey questions were developed following an initial review of existing vaccine hesitancy surveys, as well as consultations within the WG as well as with SAGE members. In addition, the researchers explored proposed vaccine hesitancy questions for inclusion in the World Health Organization (WHO)-United Nations Children's Fund (UNICEF) Joint Reporting Form (JRF) on immunisation, which are completed by national immunisation programme managers annually to capture the nature and scope of vaccine hesitancy at the national level. As part of the national JRFs completed annually, two indicators for vaccine hesitancy were pilot-tested in the Americas and the European WHO regions. The two indicators were also tested in a self-administered questionnaire distributed at the East, South, and Central African Regional Immunization Managers' meetings in 2013.

The response rate to the first JRF pilot in 2012 was sub-optimal, with only 14% (13/94) of countries completing the questions. 2013 JRF indicator revisions included:

• regarding reasons for vaccine hesitancy: Question 1: What are the top three reasons for not accepting vaccines according to the national schedule? Question 2: Is this response based on or supported by some type of assessment, or is it an opinion based on your knowledge and expertise?
• regarding process indicators: Question 1: Has there been some assessment of vaccine hesitancy or refusal among the public at the national or sub-national level? Question 2: If yes, please provide assessment title(s) and reference(s) to any publication/report.

Parallel to the piloting of questions in the JRF, additional survey questions were collected to inform a more detailed survey tool. Then, a review was undertaken to identify all survey questions and tools mentioned in the articles collected in a systematic review of literature conducted on vaccine hesitancy. A selection of articles (n = 2,933) were re-screened for this purpose.

The top three reasons for vaccine hesitancy reported in the 2013 JRF, which enjoyed higher reporting rates, were: (i) beliefs, attitudes, and motivation about health and prevention, (ii) risk/benefit of vaccines, and (iii) communication and media environment. Major issues were fear of side effects of vaccination and distrust in the vaccine, lack of perceived risk of vaccine-preventable diseases and the influence anti-vaccination reports in the media.

In developing the survey tool, the researchers reviewed 108 articles, 10 of which included complete survey tools on vaccine hesitancy, confidence, or trust. "The work of Opel et al. was among the first to develop and validate a survey tool specific to vaccine hesitancy, the Parent Attitudes About Childhood Vaccines (PACV) survey. The PACV was originally developed by adapting items from previous surveys on health beliefs, conducting focus groups to produce additional items, submitting these items to a panel of immunization experts to remove items unlikely to be useful, and pre-testing the product on a group of parents. The result of this process was an 18-item survey encompassing the domains: immunization behaviour, beliefs about vaccine safety and efficacy, attitudes and trust." The WG adapted this set of questions to have more global relevance, given that the tool was developed and validated for a high-income setting (see Table 1).

"The review of vaccine hesitancy research to identify specific survey questions revealed that much of the research on this topic is largely on cognition-based features such as knowledge, attitudes and beliefs and draws on two commonly used health behaviour models: the Health belief Model and the Theory of Planned Behaviour. Neither of these models adequately investigate the significance of social, economic and/or environmental factors as determinants of health behaviour, in this case vaccine hesitancy. Questions that were identified through the literature search were then mapped against the key determinants identified (Table 2 [e.g., "When you hear a negative comment about vaccine(s), do you: Ask a friend what they think? Ask a health worker? Ask a family or other relative? Go to the internet? Other?"], Table 3 [e.g., "Do you think the polio vaccine is still needed?"] and Table 4 [e.g., "What is the first thing you want to know when a new vaccine is introduced or announced?"]) based on feedback from the Working Group, and were presented at a meeting on December 2013 for further discussion and feedback. It was clear that a number of determinants of vaccine hesitancy were not adequately addressed in the identified survey questions documented in the literature review. It was also agreed that while the matrix was a useful approach to identifying gaps in the questions, a more survey-ready format was needed for implementation."

The WG developed a compendium of three different types of survey questions (See Appendices): Core Closed Questions (Appendix A); Likert Scale Questions (Appendix B); and a set of Open Ended Questions (Appendix C). Some were derived from previously validated questionnaires, albeit in high-income countries only, some came from experts in the field, and others are newly proposed.

The researchers conclude: "Given the dynamic and changing nature of vaccine hesitancy, the importance of ongoing monitoring cannot be overstated. A survey which reveals little hesitancy this year may have a different result next year. These trends need monitoring. Additionally, qualitative research to better understand the contextual and socio-cultural influences that may be contributing to vaccine hesitancy will be important in informing the most relevant strategies to engage hesitant publics, health providers and policy makers."