Framing messages for vaccination supporters

Efficiently communicating information on vaccination is crucial to maintaining a high level of immunization coverage, but it implies finding the right content for the right audience. Pro- vaccination individuals, who represent the majority of the population, and who have been neglected in the literature, could play an important role relaying pro-vaccination messages through informal discussions, if only these messages are (i) found plausible, (ii) remembered, and (iii) shared. We conducted seven experiments on 2761 pro-vaccination online participants (U.S. and U.K.), testing whether the valence of a statement (positive or negative) and its rhetorical orientation (pro- or anti-vaccine) affected these three steps. Participants deemed more plausible, were more willing to transmit (and actually transmitted more), but did not remember better positively framed statements. Pro-vaccination rhetorical orientation had little or no effect. Overall, the framing effects observed were dramatic: one framing made participants very eager to transmit a statement, while another made them reluctant to transmit it at all. The framing effects also influenced vaccination attitudes, with participants exposed to positively framed statements reporting more positive attitudes toward vaccination. Since messages have to be framed one way or the other, the framing effects demonstrated here should be considered when designing public health messages.