When taking action means accepting responsibility: Omission bias predicts parents' reluctance to vaccinate due to greater anticipated culpability for negative side effects

Omission bias is the tendency to consider harm from inaction preferable to equivalent harm from action. In this work, we explored how individual differences in omission bias shape parental vaccine-related decisions. Parents with a stronger omission bias showed greater negative emotional response to physician vaccine policy, placed lower trust in medical providers, and assigned a lower priority on vaccination. We observed this pattern of results even among parents who prioritize vaccination. Heightened anticipation of moral culpability for action (e.g., a child experiences vaccine side effects) and a diminished anticipation of moral culpability for possible harms of not acting (e.g., a child contracts a vaccine-preventable disease) accounted for the effects we observed. These results suggest that parents' reluctance to vaccinate their children stems—in part—from the heightened perceived moral culpability that comes with taking action (versus not taking action).