Online commenters have a bigger impact on individuals’ opinions on vaccines than credible public service announcements (PSAs), according to researchers from Washington State University (WSU).

Lead researcher Ioannis Kareklas, PhD, assistant professor of marketing at WSU, told Pharmacy Times about the surprising results, which were published in the Journal of Advertising.

Although the study participants did not have any information on which to judge the credibility of a commenter posting about vaccinations, they were just as influenced by unknown and presumably nonexpert online commenters as they were by PSAs designed to look as though they were distributed by the US Centers for Disease Control and Prevention (CDC). 

“This finding was quite surprising to us and was the impetus for our subsequent research investigation,” Dr. Kareklas told Pharmacy Times.

The first study used phony PSAs from the CDC, representing the pro-vaccination side, and the National Vaccination Information Center, reflecting the anti-vaccination side. Each of the PSAs also had online comments from 4 individuals that championed or discredited vaccinations. The researchers ensured that the names of the fake commenters were unisex so that a gender bias would not affect the results.

After 1 minute, the participants answered a couple of questions about their thoughts on what it would mean to vaccinate themselves or their family members. The answers they could choose from came in pairs: good or bad, foolish or wise, unsafe or safe. The participants were also asked how credible the PSAs and online commenters were.

Despite the fact that the commenters had no expert knowledge, both the commenters and the PSAs equally persuaded the participants.

In the second study, participants read messages from 3 different fake commenters: a medical doctor in the field of infectious diseases and vaccinology, a lobbyist with a focus on health care, and an English major.

Unsurprisingly, the participants valued the opinion of the physician over the others on the topic of vaccinations. More surprising was the fact that the doctor’s opinion in the comments persuaded participants more than the PSAs.

Dr. Kareklas suggested that websites like WebMD, which may see discussions about vaccines breeding, not only allow for such discourse to take place, but also ensure that pro-vaccine comments from experts are easily accessible and visible. The researchers did not think that websites should take down comments from anti-vaxxers.