COVID-19 hoax belief endorsement and its implications for vaccine uptake: Investigating the role of perceived threat.

Belief that COVID-19 was a hoax has been associated with lower vaccine uptake, potentially due to reduced perceptions of disease threat. Using longitudinal data from a community sample (N = 1058), we tested whether perceived threat mediated the relationship between hoax belief and vaccine uptake, and whether this relationship varied by level of perceived threat. Counterfactual mediation analysis indicated that hoax belief predicted lower vaccine uptake in part through diminished perceived threat. However, hoax belief also had a direct negative effect on vaccine uptake-but only when perceived threat was low. These findings highlight the dual role of perceived disease threat, functioning both as a mechanism linking belief to behavior and as a contextual factor shaping the strength of that association. Recognizing this nuance in the effects of conspiracy belief endorsement is critical for developing public health communication strategies that are credible in content and effective across ideological divides.