Effects of Framing Side-Effect Risks for a Hypothetical Vaccine: A Discounting Approach

Probability discounting describes the systematic decrease in subjective value as the probability of an undesirable outcome increases. The present study examined whether hypothetical vaccine acceptance varies as a function of communicated side-effect risk and whether this relation is influenced by framing format. 35 undergraduates provided Likert-scale acceptance judgments across multiple levels of side-effect risk presented under either absolute or relative framing conditions. Acceptance decreased monotonically with increasing risk, and aggregate data were well described by a generalized hyperbolic function, consistent with established models of probability discounting. Framing systematically altered the relation between communicated risk and acceptance, with relative framing showing greater sensitivity to individual baseline risk estimates. These findings suggest that framing may function as a contextual variable that modulates the transformation of probabilistic information into subjective value. Although individual-level variability was observed, the overall pattern suggests that probability discounting provides a useful framework for analyzing acceptance decisions about vaccination involving probabilistic harm. The present judgment-based procedure may offer a complementary method for examining probability discounting across framing conditions and decision contexts.