Trends in Classifying Vaccine Hesitancy Reasons Reported in the WHO/UNICEF Joint Reporting Form, 2014-2017: Use and Comparability of the Vaccine Hesitancy Matrix

"The need to understand the drivers of global vaccine hesitancy is perhaps more crucial than ever as the world gears up to introduce COVID-19 vaccines..."

Recent outbreaks of vaccine-preventable diseases (VPDs) around the globe have been partly attributed to a rise in vaccine hesitancy, thereby highlighting the significance of caregivers' decision to delay or refuse vaccines for their children. Since 2014, the World Health Organization (WHO) member states have been annually reporting vaccine hesitancy reasons on the WHO/United Nations Children's Fund (UNICEF) Joint Reporting Form (JRF). The Vaccine Hesitancy Matrix (VHM), developed by the WHO Strategic Advisory Group of Experts on Immunization (SAGE) Vaccine Hesitancy Working Group, can serve as a tool to categorise vaccine hesitancy reasons reported in the JRF. This paper explores the reasons for vaccine hesitancy reported globally from 2014 to 2017 in order to ascertain trends over time and understand the comparability of using the VHM to classify hesitancy reasons from 2014 to 2016 based on previously published literature.

The researchers conducted a quantitative content analysis to code and categorise vaccine hesitancy reasons reported in the JRF from 2014 to 2017, during which time 79% to 83% of the 194 member states completed the vaccine hesitancy section of JRF each year.

The analysis showed that vaccine hesitancy trends were consistent from 2014 to 2017, where vaccine hesitancy reasons were mainly related to the 3 VHM categories of "individual and group level influences" (59%), such as lack of knowledge/awareness about vaccination services, beliefs/attitudes about health, and perceptions of vaccination risks and benefits. These reasons were followed by "contextual influences" (25%), such as reasons linked to religious, cultural, and socioeconomic factors, as well as negative historical influences and the communication and media environments. Finally, "vaccine- or vaccination-specific issues" related to, for example, the design of vaccination programmes, the role of healthcare professionals, and the lack of flexibility in the vaccination schedule accounted for 16% of the reasons.

Comparability of using the VHM to categorise vaccine hesitancy to the previously published JRF data showed that results were mostly but not entirely consistent. Major differences in categorising vaccine hesitancy were noted between 2 specific reasons - "experience with past vaccination" (under "individual and group influences") and "risk/benefit - scientific evidence" (under "vaccine and vaccination-specific issues"); this difference was usually due to lack of clear definitions in some sub-categories and generic responses reported in the JRF.

In short, the findings "demonstrate the need to address the diverse behavioral and social factors that influence vaccination decisions and experiences at both the individual and contextual levels....[T]he media environment coupled with influential leaders, gatekeepers, and vaccine lobbies were among the leading contextual influences reported by the member states; this calls for more effective strategies to address emerging and existing misinformation about vaccination services that often spread through social networks....Furthermore, the diversity of responses provided as the reasons for vaccine hesitancy more broadly suggest a complex interplay of localized and context-specific drivers of vaccination demand that need to be addressed with more tailored approaches..."

In the interest of improving data quality, the researchers offer some recommendations for modifications to the JRF hesitancy module. For example, the brevity of country-level responses to open-ended questions about reasons for vaccine hesitancy in the JRF suggests that pre-categorised response options of the commonly reported reasons could be more fruitful. A combination of multiple-choice and a few open-ended questions may yield more detailed vaccine hesitancy information. A structured format with prompts and follow-up instructions to elicit specific responses may also improve data quality.

Writing during the time of the COVID-19 pandemic and its "infodemic climate", the researchers note that this information ecosystem "underscores the persistent complexities in how perceptions and attitudes toward vaccines and vaccinations are formed, and how such perceptions can be even more complex during health emergencies." In light of the introduction of COVID-19 vaccines, they propose that the JRF could be modified - e.g., with ad-hoc modules with brief items - to collect snapshot data on country-level drivers of accepting or refusing new vaccines. "Using VHM to then classify drivers of vaccine hesitancy for new vaccine may help in vaccine introduction planning, preparedness and response through tailored communication and policies."

In conclusion, the cumulative reasons provided for vaccine hesitancy across the 194 member states in the JRF suggest that there are a multitude of factors influencing vaccination behaviours that can inform targeted intervention approaches.