How Does Communicating Herd Immunity Affect Immunization Intentions?

While previous studies have shown that communicating herd immunity can increase immunization intentions, it is unclear how the definition of beneficiaries influences intentions. In a vignette study, using new hypothetical influenza virus, 4,172 participants from five European countries (Bulgaria, N=873; Denmark, N=896; England, Estonia, N=916; and Italy, N=745) were randomized to one three experimental conditions: (1) control (no mention immunity), (2) society (social benefit for overall mentioned), (3) friends family members mentioned). study did not find influenced intentions across countries, found substantial cross-country differences in effect communication. increased while Denmark but decreased Italy. social influence its contrasting effects highlight importance empirically testing.