Countering Antivax Misinformation via Social Media: Message-Testing Randomized Experiment for Human Papillomavirus Vaccination Uptake

"[H]arnessing social media platforms for public health communications, directly countering dominant misinformation themes and providing accurate science-based information can be particularly effective in promoting HPV vaccination uptake."

Since the human papillomavirus (HPV) vaccine was approved in 2006, the prevalence of misinformation on social media and the lack of educational campaigns regarding HPV vaccines have contributed to HPV vaccine hesitancy and refusal in countries such as the United States (US). This study compared different message themes related to HPV vaccine hesitancy and refusal and examined the themes and messages that were more effective in changing US parents' attitudes and behavioural intentions toward HPV vaccination.

First, the researchers conducted a series of virtual focus groups with US parents to identify the key barriers and reasons for HPV vaccine hesitancy and refusal. They identified 5 salient themes to address in the study's messages on HPV vaccination: (i) safety, side effects, risk, and ingredient concerns and long-term or major adverse events; (ii) distrust of the healthcare system; (iii) HPV vaccine effectiveness concerns; (iv) connection to sexual activity; and (v) misinformation about HPV or HPV vaccine. They developed 5 experimental messages for each theme and 6 control messages on e-cigarettes. Grounded in scientific information from published articles and reputable health organisations, the experimental messages were designed to help the audience understand HPV and HPV vaccination and included a call to action to vaccinate their children against HPV.

Among the 1,713 participants recruited via social media and crowdsourcing sites, 1,043 eligible parents completed a pretest survey questionnaire. Participants were then randomly assigned to 1 of the 31 messages and asked to complete a posttest survey questionnaire that assessed attitudes toward the HPV vaccine and perceived effectiveness of the viewed message. A subgroup of participants (189/995, 19%) with unvaccinated children aged 9 to 14 years was also assessed for their behavioural intention to vaccinate their children against HPV.

The study found that parents in the experimental group had increased positive attitudes toward HPV vaccination compared with those in the control group (t969=3.03, P=.003), which was associated with increased intention to vaccinate among parents of unvaccinated children aged 9 to 14 years (r=1.14, P=.05). Four themes (themes ii-v) were relatively effective in increasing behavioural intentions by positively influencing attitudes toward the HPV vaccine. On the message level, messages that provided scientific evidence from government-related sources (e.g., the Centers for Disease Control and Prevention, or CDC) and corrected misinformation (e.g., "vaccines like the HPV vaccine are simply a way for pharmaceutical companies to make money. That isn't true.") were effective in forming positive perceptions toward the HPV vaccination messages.

Certain messages within each thematic block were more effective than other messages in generating positive perceptions of the message viewed. For example, messages that provided numeric evidence from credible sources (e.g., "As you will hear in this video from the Minnesota Department of Health...") were perceived more persuasive than messages that did not refer to a credible source (e.g., "The vaccine's safety has continued to be studied in the 12 years..."). Notably, no message generated adverse effects or boomerang effects of persuasion, such as stimulating the opposite stance.

Thus, this study demonstrated that systematic designs of communication themes and message components not only influence overall parental attitudes and evaluations of the messages but also can positively change behavioural intention toward HPV vaccination for unvaccinated children. The researchers point out that "digital technologies, including social media, are ubiquitous in promoting public health, even among often hard-to-reach populations such as rural residents.... [This] study indicates that social technologies can be leveraged to deliver strategic public health communications to people who may have limited health care resources to intervene in their behaviors and improve their attitudes toward the HPV vaccine."

In conclusion: "Evidence-based messages directly countering misinformation and promoting HPV vaccination in social media environments can positively influence parents’ attitudes and behavioral intentions to vaccinate their children against HPV."