Highlighting consensus among medical scientists increases public support for vaccines: evidence from a randomized experiment

BACKGROUND: A substantial minority of American adults continue to hold influential misperceptions about childhood vaccine safety. Growing public concern and refusal to vaccinate poses a serious public health risk. Evaluations of recent pro-vaccine health communication interventions have revealed mixed results (at best). This study investigated whether highlighting consensus among medical scientists about childhood vaccine safety can lower public concern, reduce key misperceptions about the discredited autism-vaccine link and promote overall support for vaccines. METHODS: American adults (N = 206) were invited participate in an online survey experiment. Participants were randomly assigned to either a control group or to one of three treatment interventions. The treatment messages were based on expert-consensus estimates and either normatively described or prescribed the extant medical consensus: “90 % of medical scientists agree that vaccines are safe and that all parents should be required to vaccinate their children”. RESULTS: Compared to the control group, the consensus-messages significantly reduced vaccine concern (M = 3.51 vs. M = 2.93, p < 0.01) and belief in the vaccine-autism-link (M = 3.07 vs M = 2.15, p < 0.01) while increasing perceived consensus about vaccine safety (M = 83.93 vs M = 89.80, p < 0.01) and public support for vaccines (M = 5.66 vs M = 6.22, p < 0.01). Mediation analysis further revealed that the public’s understanding of the level of scientific agreement acts as an important “gateway” belief by promoting public attitudes and policy support for vaccines directly as well as indirectly by reducing endorsement of the discredited autism-vaccine link. CONCLUSION: These findings suggest that emphasizing the medical consensus about (childhood) vaccine safety is likely to be an effective pro-vaccine message that could help prevent current immunization rates from declining. We recommend that clinicians and public health officials highlight and communicate the high degree of medical consensus on (childhood) vaccine safety when possible. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12889-015-2541-4) contains supplementary material, which is available to authorized users.