Highlighting Consensus Among Medical Scientists Increases Public Support for Vaccines

Evidence From a Randomized Experiment

Sander L. van der Linden; Chris E. Clarke; Edward W. Maibach


BMC Public Health. 2015;15(1207) 

In This Article


Vaccines are one the most effective global public heath interventions, saving millions of lives every year.[1] Although childhood immunization rates in the U.S. are at a historic high[2] and there is widespread agreement among medical scientists about the safety and public health benefits of approved vaccines,[3,4] the number of American adults who report having heard "a great deal" about the disadvantages of vaccines for children has nearly doubled in the last 14 years (to 30 %), and over 52 % currently report being "unsure" whether certain vaccines cause autism.[5,6] In addition, a recent national survey revealed that in a typical month, over 90 % of US physicians now frequently receive requests to "delay" child vaccines.[7] Growing concern about vaccines can erode public support and result in decreased immunization rates and recurrence of (preventable) life-threatening diseases[8] (e.g., the 2015 measles outbreak).

Systematic evaluations of public health communication strategies that focus on vaccine promotion range from being largely inconclusive about their general effectiveness[9,10] (at best) to revealing that some messaging strategies may be counter-productive[11,12] (at worst), especially among vaccine hesitant audiences.[13] One prominent issue is that media journalists frequently report arguments for and against vaccine safety in a "balanced" fashion that fails to emphasize the extant medical consensus.[14] This is important because recent research has found that communicating scientific consensus about vaccine safety attenuates perceptions of scientific uncertainty regarding vaccine risk.[15,16] Moreover, for other contentious issues like climate change, public perception of the level of scientific agreement has shown to act as an important "gateway cognition," influencing other key beliefs about the issue as well as support for action.[17–20] Highlighting consensus is thought to be particularly effective because it describes an important social norm within a community, which people often use as a heuristic to guide their beliefs and judgments on the issue.[17,18] Consensus heuristics are efficient because they reduce the cost of individual learning by condensing a complex amount of information into a simple normative fact (e.g., 90 % of medical experts agree that vaccines are safe). This study examines whether highlighting the medical consensus on vaccine safety can increase public understanding of the scientific consensus, and, in turn, reduce misperceptions about the discredited autism-vaccine link and promote pro-vaccine attitudes, norms, and intentions.