Unpacking Effects of Perceived Familiarity with COVID-19 Vaccine Misinformation on Message Perceptions, Affects, and Determinants of Vaccination: A Moderation Analysis of Two Types of Message Features

Abstract

The proliferation of health misinformation poses a significant threat to public health, making it increasingly important to understand why misinformation is accepted. The illusory truth effect, which refers to the increased believability of a message due to repeated exposure, has been widely studied. However, the specific influence of perceived familiarity with vaccine misinformation on message perceptions, emotional responses, and vaccination behavior determinants remains underexplored in the context of COVID-19 vaccine misinformation. The dissertation seeks to fill the gap and further examines whether misinformation message features, including source credibility and evidence types, affect the magnitude of effects of perceived familiarity with COVID-19 vaccine misinformation. The findings from two experimental studies suggest that perceived familiarity enhanced perceived accuracy and agreement with COVID-19 vaccine misinformation, lessened confusion about the misinformation, and reduced the intention to verify the misinformation. Source credibility intensified perceived accuracy and emotional distress but did not interact with perceived familiarity to affect message perceptions, affects, and determinants of vaccination behavior. Regarding evidence types employed by vaccine misinformation, statistical and combined evidence types were more effective than narrative evidence in enhancing perceived message effectiveness, eliciting negative emotions, and increasing information verification intentions. Furthermore, evidence type did not moderate the effects of perceived familiarity on outcome variables, with one exception: confusion. The dissertation adds to the literature on the illusory truth effect in the sense that source credibility and evidence type do not moderate the effects of perceived familiarity with COVID-19 vaccine misinformation on message perceptions, vaccine attitudes, and vaccination intentions. These findings reinforce the robustness of familiarity effects or the illusory truth effect; even message features cannot moderate the effects. This dissertation calls for further research into interventions that can mitigate the familiarity effects of health misinformation and explores strategies that leverage perceived familiarity to enhance the dissemination of accurate health information.