BOULDER, Colo. — Anti-vaccination sentiment has been building in the United States over the past five years, with Twitter being one of the most instrumental vehicles for those who oppose traditional vaccines, a new study finds.
Using a machine-learning algorithm, researchers from the University of Colorado and the University of Alabama analyzed more than 500,000 tweets from across the U.S. between 2009 and 2015. The researchers limited their range to only include tweets that mentioned autism and vaccines.
The belief that vaccinations can cause autism comes from a 1998 study of 12 children that suggested links between the measles, mumps, and rubella vaccine and a predisposition to developmental disorders in children. The journal that published the study, The Lancet, retracted the study in 2010. Several subsequent studies probing for links between vaccines and autism have failed to produce any evidence.
Yet the debate rages on online.
“The debate online is far from over. There is still a very vocal group of people out there who are opposed to vaccines,” says Chris Vargo, one of the study’s co-authors, in a university release. “Half of the talk online that we observed about vaccines was negative.”
Though the vast majority of doctors urge patients to continue to have their children receive regular immunizations, the anti-vaxxer movement may be stronger than one might think. With the study showing that tweets supporting anti-vaxxers became more frequent during the sample period, the authors point to multiple recent outbreaks of previously vaccine-preventable diseases in recent years because of anti-vaccination beliefs. Only a few small studies have attempted to learn what is fueling these beliefs.
As for what the authors learned about anti-vaxxers who are espousing their beliefs on Twitter, the study finds affluent regions or areas with large numbers of new mothers seemed to have the largest quantities of anti-vaccine tweets. Particularly households that see an income of at least $200,000 were more likely to buy into the movement.
The authors caution, however, that the tweets didn’t necessarily represent an accurate sample of overall public opinion, but it did allow researchers a glimpse into smaller areas where anti-vaxxers are more prevalent.
“Unfortunately, the idea is still very much out there, being promoted by a vocal minority online,” says co-author Theodore Tomeny, an autism researcher with University of Alabama. “That’s problematic because often only one side of the story is being told.”
The full study was published in the journal Social Science and Medicine.