The impact of (un)certainty information and source expertise on risk perception and vaccination decision making

  • F. Mevissen
  • V. Visschers


Background: People often make health-related decisions (e.g. to undergo medical treatment or not) based on (risk) information that includes ambiguous information from different, conflicting sources. However, ambiguous information is distrusted which in turn influences risk perceptions and decision-making. We explored how (un)certainty in information regarding vaccination efficacy and source expertise influence risk perception and decision making regarding vaccination to prevent Lyme disease. Methods: Participants (N = 190; 63.5% female, Mage = 58.4) of an online Swiss panel were randomly distributed in a between subjects 2(Information: certain vs uncertain) x 2(source: expert vs. lay) design. All participants read a (fake) newspaper article on Lyme disease, including information on symptoms and consequences. They were then offered additional information from either an internet forum or a medical information website (manipulation of source of information: expert vs. lay). The information they received communicates about the efficacy of the vaccine in a certain way (80% effective) vs in an uncertain way (70-90% effective). Main outcome measures included risk perception, vaccination efficacy, vaccination intention and measures evaluating the information. Findings: No information x source interaction effects were found on the main outcome measures (p’s > .11). Main effects of source showed that people rate the efficacy of the vaccine higher (p < .05) and the perceived uncertainty lower (p < .001) if the message comes from an expert. Discussion: The finding that information from experts is still rated more positively is promising. The lack of interaction effects is likely explained by a too small uncertainty range.
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