Vaccine Hesitancy in Online Spaces: A Scoping Review of the Research Literature, 2000-2020

"The core takeaway of this review is that research on vaccine hesitancy in online spaces would benefit from the continued and strengthened participation of disciplines that can offer a range of research approaches to online communication dynamics..."

Though vaccine hesitancy, misinformation, and online environments offer different sets of issues, health officials and researchers acknowledge overlaps, as achieving broad acceptance of vaccines requires understanding information ecosystems. To that end, this article reviews 100 articles published from 2000 to early 2020 that explore aspects of vaccine hesitancy in online communication spaces and identifies several gaps in the literature that suggest future research needs/directions.

As the review unearthed, in the early 2000s, researchers studied vaccine information on websites and even at this early stage noted the spread of anecdotal accounts of vaccine dangers and the misrepresentation of the science behind vaccines. Search results show that the relationship between online vaccine hesitancy and the quality of online information was a persistent concern in the research literature at that time, and the review frequently encountered articles referencing "misinformation" or expressing concerns about the accuracy of information.

With the emergence of participatory websites and technologies enabling internet users to generate content and interact with each other via social media, researchers in the 2010s increasingly examined the sources of information about vaccines and network dynamics that help these sources spread information. The central finding was that vaccine hesitancy was prevalent online but often circulated in small but active and cohesive subgroups of internet users. Researchers also increasingly recognised nuances among different forms of vaccine hesitancy and explored the power of storytelling as opposed to the use of facts and statistics prevalent on official health sites.

As the years passed, researchers increasingly urged monitoring and moderating social media platforms to stop the spread of misinformation, offering recommendations for action such as: enhancing surveillance of misinformation; removing sources, as well as information; stepping up platform self-regulation; and engaging lawmakers, activists, and others in policy interventions. Despite this emphasis on platforms, the literature most often identified health authorities and professionals as top stakeholders in addressing vaccine hesitancy and online misinformation. Proposed actions for this category of stakeholders include getting involved in online groups that spread misinformation, including stories alongside scientific facts in communication efforts, and adopting "vaccine ambassador" programmes, in which community members or health professionals share reliable information with select audiences to promote vaccine confidence and adherence.

The review identifies gaps in the literature in areas including: disciplinary focus; specific vaccine, condition, or disease focus; stakeholders and implications; research methodology; and geographical coverage. For example, most articles reviewed were conducted by Western research institutions and focused on vaccine hesitancy within Western contexts. Such strategies may be inappropriate in regions grappling with diseases not prominent in the West, such as polio. Also, few of the articles made causal inferences.

Directions for future research - beyond examining how the COVID-19 pandemic has changed the state of this research - include:

• Conduct interdisciplinary comparative research on online vaccine hesitancy across national, regional, local, and cultural contexts. The review noted that research has over the years begun to engage more with the online sources of information rather than the quality of the information itself; interdisciplinary, comparative research is capable of bringing into view an additional set of structural sources or influences that can be addressed through policy interventions.
• Carry out qualitative, ethnographic fieldwork: The review shows that the most prominent focus of research to date has been on information-sharing behaviours rather than the identities of those who share information, including social milieus important to those identities. Ethnographic fieldwork is capable of enhancing understanding of how vaccine hesitancy relates, on a day-to-day basis, to a variety of social factors, and how these factors relate to the online sharing of vaccine information. This fine-grained, nuanced fieldwork could inform intervention strategies.
• Undertake more research on different communities' vulnerability to vaccine misinformation, as well as where and how they encounter it. Investigations into the role of gender, race, religious/spiritual beliefs, and political ideology could highlight different online information pathways. Understanding the intersections between various communities is important when it comes to effective communication and outreach.
• Conduct longitudinal research in order to highlight changes over time, identify patterns and discursive moments, and assess the impact of platform actions such as de-platforming bad actors.
• Address the broad, persistent issue of constraints on researcher access to online spaces and the challenges posed by frequently changing data formats and algorithms. There is typically silence in the literature around these ubiquitous issues; by cataloging how researchers have encountered and addressed them, future literature reviews could contribute to the development of better research strategies and methods.