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Opinions on Vaccines Strongly Influenced by Online Comments

In a new study, researchers investigated how comments on the Internet tend to affect people’s opinions on whether or not childhood vaccines should be enforced. With some still fearing that vaccines have an impact on autism development, the subject is becoming more emotionally charged as measles has been re-emerging as a threat.

Although healthcare websites have been updated with current advertisements about health risks for the unvaccinated, researchers from Washington State University say that people may be influenced more by online comments than by official public service announcements (PSAs).

The study, entitled “Reexamining Health Messages in the Digital Age: A Fresh Look at Source Credibility Effects,” comes after a recent outbreak of measles linked to Disneyland parks in California which has affected at least 100 people in the United States and Mexico. It is the first study to investigate how Internet comments from individuals whose expertise is unknown impact the way people feel about vaccines.

“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 marketing researcher Ioannis Kareklas and colleagues in the Journal of Advertising.

Kareklas, and co-researchers Darrel Muehling and T.J. Weber conducted two experiments.

In the first, they showed 129 participants two fictitious PSAs. Participants were told that the pro-vaccination PSA was sponsored by the U.S. Centers for Disease Control and Prevention (CDC), while the anti-vaccination PSA was sponsored by the National Vaccine Information Council (NVIC). To enhance validity, both made-up PSAs were designed to look like they appeared on each organization’s respective website.

The PSAs were followed by comments from fictitious online commenters who either expressed pro- or anti-vaccination viewpoints. Participants weren’t told anything about who the commenters were, and unisex names were used to avoid potential gender biases.

After looking at the false PSAs and comments, participants completed questionnaires that rated their likelihood to vaccinate themselves and their family members, as well as their opinions about vaccination.

The researchers found that the participants were equally persuaded by the PSAs and the online comments. “That kind of blew us away,” said Kareklas. “People were trusting the random online commenters just as much as the PSA itself.”

In the second experiment, participants were told 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 findings showed that the participants gave more sway to the doctor’s comments than the PSAs.

“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.

The results offer some valuable insight into why the anti-vaccination movement has been so influential. 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.

Kareklas noted three instances in which popular sites including Science, the Huffington Post and the Chicago Sun Times have banned anonymous online comments because they feel people are discrediting proven science.

“We don’t subscribe to the practice of taking down comments,” he said, “because managers would also lose credibility if they only posted positive comments.”

The researchers suggest that social advertisers need to be strongly aware that their attempts to persuade are not perceived by readers as being manipulative or disingenuous. Health websites should include opposing viewpoints where relevant, but should also ensure that supportive comments are in abundance, readily accessible and supported by research evidence.

“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.

Finally, 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.”

Source: Washington State University

Girl getting a shot photo available from Shutterstock

Opinions on Vaccines Strongly Influenced by Online Comments

Traci Pedersen

Traci Pedersen is a professional writer with over a decade of experience. Her work consists of writing for both print and online publishers in a variety of genres including science chapter books, college and career articles, and elementary school curriculum.

APA Reference
Pedersen, T. (2018). Opinions on Vaccines Strongly Influenced by Online Comments. Psych Central. Retrieved on September 30, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 6 Feb 2015)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
Published on Psych All rights reserved.