Including "evidentiary balance" in news media coverage of vaccine risk.

Journalists communicating risk-related uncertainty must accurately convey scientific evidence supporting particular conclusions. Scholars have explored how "balanced" coverage of opposing risk claims shapes uncertainty judgments. In situations where a preponderance of evidence points to a particular conclusion, balanced coverage reduces confidence in such a consensus and heightens uncertainty about whether a risk exists. Using the autism-vaccine controversy as a case study, we describe how journalists can cover multiple sides of an issue and provide insight into where the strength of evidence lies by focusing on "evidentiary balance." Our results suggest that evidentiary balance shapes perceived certainty that vaccines are safe, effective, and not linked to autism through the mediating role of a perception that scientists are divided about whether a link exists. Deference toward science, moreover, moderates these relationships under certain conditions. We discuss implications for journalism practice and risk communication.