Two groups are responsible for more than half of the anti-vaccine ads spreading misinformation on Facebook, according to a study published in Vaccine.
Researchers analyzed data on 309 vaccine-related ads housed in Facebook's Ad Archive on Dec. 13, 2018, and Feb. 22, before the company updated its policy on anti-vaccine advertising in March, reports The Washington Post.
They found two groups purchased 54 percent of anti-vaccine ads on Facebook: the World Mercury Project, led by Robert F. Kennedy Jr., and Stop Mandatory Vaccination. In contrast, pro-vaccine ads came from a much more diverse set of buyers.
The results are surprising, as many anti-vaccine posts on social media platforms appear to be grassroots messages from parents and community groups, researchers told The Washington Post.
"In fact, what we are seeing is a small number of motivated interests that are trying to disseminate a lot of harmful content," study author David Broniatowski, PhD, an associate professor at George Washington University in Washington, D.C., told the publication.