Communication of Scientific Uncertainty about a Novel Pandemic Health Threat: Ambiguity Aversion and Its Mechanisms.

Communicating scientific uncertainty about public health threats is ethically desirable but challenging due to its tendency to promote avoidance of choice options with unknown probabilities-a phenomenon known as "ambiguity aversion." This study examined this phenomenon's potential magnitude, its responses to different communication strategies, and its mechanisms. In a factorial experiment, 2701 adult laypersons in Spain read one of three versions of a hypothetical newspaper article describing a pandemic vaccine-preventable disease (VPD), but varying in scientific uncertainty about VPD risk and vaccine effectiveness: No-Uncertainty, Uncertainty, and Normalized-Uncertainty (emphasizing its expected nature). Vaccination intentions were lower for the Uncertainty and Normalized-Uncertainty groups compared to the No-Uncertainty group, consistent with ambiguity aversion; Uncertainty and Normalized-Uncertainty groups did not differ. Ambiguity-averse responses were moderated by health literacy and mediated by perceptions of vaccine effectiveness, VPD likelihood, and VPD severity. Communicating scientific uncertainty about public health threats warrants caution and further research to elucidate its outcomes, mechanisms, and management.