With the recent comeback of measles and other vaccine-preventable diseases in the United States, health professionals and journalists have ramped up their efforts to educate the public about the safety and effectiveness of childhood immunizations. But in the fierce debate over vaccinations, trusted doctors and experts may be no match for the loud and often inaccurate wisdom of Internet commenters, according to a new study.
When presented with mock public service announcements (PSA’s) from the Centers for Disease Control and Prevention (CDC) or the anti-vaccination group National Vaccine Information Center (NVIC), study volunteers found the information persuasive. However, advice from random online commenters was just as influential, the researchers found.
“That kind of blew us away,” said Dr. Ioannis Kareklas, the study’s lead author. “People were trusting the random online commenters just as much as the PSA itself.”
The findings, which will appear in an upcoming issue of the Journal of Advertising, underscore the powerful influence of information disseminated by word of mouth. Moreover, they offer striking insight into the ability of the anti-vaccination movement to flourish even in the face of mounting public outrage and overwhelming scientific evidence that unequivocally supports vaccination.
For the study, “Reexamining Health Messages in the Digital Age: A Fresh Look at Source Credibility Effects,” the researchers performed two experiments. In the first, they showed 129 participants one of two mock PSA’s: One made the case for vaccination and was presented as coming from the CDC, while the other argued against vaccination, and came from the anti-vax group NVIC. The PSAs were followed by comments that expressed either pro- or anti-vaccination viewpoints. Participants weren’t told anything about who the commenters were or if they had any expertise in the subject area.
After looking at the PSAs and comments, people responded to questionnaires that rated their likelihood to vaccinate themselves and their family members, as well as their opinions on vaccination. The results showed that participants were just as persuaded by the PSAs as the online comments, judging both as equally credible and truthful.
In the second experiment, participants were told that the fictitious commenters were an English literature student, a lobbyist specializing in healthcare issues and a medical doctor specializing in infectious diseases and vaccinology. The results revealed that participants found the “doctor’s” comments to be more impactful than the PSAs. The statements made by commenters helped determine whether a PSA was able to persuade people that vaccination was important and whether they would be sure to vaccinate themselves and their families. In some cases, the online comments made by strangers had a greater influence than the PSAs themselves, the study found.
“We found that when both the sponsor of the PSA and the relevant expertise of the online commenters were identified, the impact of these comments on participants’ attitudes and behavioral intentions was greater than the impact of the PSA and its associated credibility,” the researchers wrote.
Word-of-mouth trumps science
The new research comes in the midst of outbreak of measles linked to Disneyland parks in California that has affected at least 100 people in the United States and Mexico, including several young infants who were too young to be vaccinated. Health officials have attributed that outbreak, and others in recent years, to a growing anti-vaccination movement in which false claims about a link between vaccines and autism have driven some parents to refuse to vaccinate their children. (For the record, no such link exists: The 1998 study that proposed such a link has been retracted by the journal that published it.
“In the context of health advertising, few issues have concerned advertisers, researchers and consumers — especially those with young children — more than recent trends in vaccination attitudes and behaviors,” wrote Kareklas and colleagues.
The study provides some valuable insight into why the anti-vaccination movement has been so persistent. As the paper points out, researchers have long known that people take word-of-mouth communications—both electronic and in person—more seriously than they do advertisements. In fact, Popular Science magazine recently stopped allowing comments because of a study from the University of Wisconsin that showed that such comments could make naive readers think that settled science is up for debate.
However, it wasn’t apparent until now that this extended to PSA’s from recognized institutions, as well. Just as people often give more credence to Yelp reviews than to restaurant ads, they may put more trust in Internet commenters they perceive to be credible than in public service announcements (or, in the case of the National Vaccine Information Center, public disservice announcements).
These findings reiterate the fact that people shouldn’t simply trust everything they read online without evaluating the credibility of the source, Kareklas said. The study also has practical implications for organizations that might try to persuade people with public service announcements.
The researchers suggest that social advertisers must be vigilant that their attempts to persuade are not perceived by readers as being manipulative or disingenuous.”We don’t subscribe to the practice of taking down comments,” said Kareklas, “because [they] would also lose credibility if they only posted positive comments.” Health websites should include opposing viewpoints where relevant, but should also ensure that supportive comments are abundant, easily accessible and supported by research evidence, the researchers said.
“It would be advisable for some supportive comments from noted experts to be highlighted on health websites,” they said. They recommended that advertisers clearly identify the expertise of the commenter — for example, a medical doctor specializing in a related field of medicine.
Most important, the researchers said social advertisers must strive to develop online media strategies that encourage “credible online exchanges where innovative thinking facilitates collaborative problem solving and results in improving customer welfare for all parties involved.”