An experimental study on the effects of electronic medicinal product information on vaccine hesitancy.

Although immunization through vaccination is one of the most successful public health interventions, coverage of some vaccination programs has decreased in recent years due to increased vaccine hesitancy. Cognitive biases have been shown to play an important role in affecting vaccine hesitancy. In this study, we conducted a randomized controlled trial (N = 2000, N = 1000 from Spain and N = 1000 from Bulgaria), where subjects were randomly assigned to one experimental condition. The experimental conditions differed by whether electronic product information (ePI) was presented to the subjects and by the type of information that was made more salient to the patient. The current study showed that the provision of digital information in the form of ePI has important consequences for achieving high vaccination rates. The main result suggests that providing vaccination information in the form of ePI can increase patients' vaccine hesitancy. This effect remained when positive and/or negative information in the ePI was made more salient to the patients. Additionally, we observe that vaccine hesitant individuals spend less time reading ePI. We conclude, by relating the current study to the relevant literature, that salience and information overload could be the main driver of vaccine hesitancy in the context of this study.