When it comes to vaccination, people are just as likely to be influenced by anonymous Internet comments as through public service announcements from health agencies, a new study suggests.
Washington State University researchers also found that people may be influenced more by online comments which were not anonymous than by credible public service announcements (PSAs).
Researchers Ioannis Kareklas, Darrel Muehling and TJ Weber are the first 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 behaviours," said Kareklas and colleagues.
Kareklas, Muehling and Weber conducted two experiments. In the first, they showed 129 participants two made-up PSAs.
Participants were led to believe that the pro-vaccination PSA was sponsored by the US Centers for Disease Control and Prevention (CDC), while the anti-vaccination PSA was sponsored by the National Vaccine Information Council (NVIC). Both PSAs were designed to look like they appeared on each organisation's respective website to enhance validity.
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 PSAs and comments, people responded to questionnaires that rated their likelihood to vaccinate themselves and their family members, as well as their opinions about vaccination.
Results showed participants were equally persuaded by the PSAs and the online comments.
"That kind of blew us away. People were trusting the random online commenters just as much as the PSA itself," said Kareklas.
In the second experiment, participants were told the fictitious commenters were an English literature student, a lobbyist specialising in healthcare issues and a medical doctor specialising in infectious diseases and vaccinology.
The researchers determined that participants found the doctor's comments to be more impactful 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 behavioural intentions was greater than the impact of the PSA and its associated credibility," the researchers said.
The research was published in the Journal of Advertising.
