Anti-vaccine sentiment thriving on Twitter: study

Anti-vaccine sentiment is alive and thriving on Twitter and other social media websites, according to a study which shows that regions with large number of new mothers are most likely to be hotbeds of tweets opposing vaccines.
In the five-year study, California, Connecticut, Massachusetts, New York and Pennsylvania showed the most negative tweets of any states in the US.
Regions with high affluence or a large number of new moms were most likely to be hotbeds of anti-vaccine Twitter users, the study found.
"The debate online is far from over. There is still a very vocal group of people out there who are opposed to vaccines," said Chris Vargo, assistant professor at University of Colorado Boulder in the US.

"Half of the talk online that we observed about vaccines was negative," said Vargo.
For the study, published in the journal Social Science and Medicine, researchers created a machine-learning algorithm to examine more than a half-million tweets from around the country between 2009 and 2015.

To make the sample a manageable size, they looked only at tweets that referred to both autism spectrum disorder and vaccines.
For two decades anti-vaccine activists have suggested that certain vaccines can lead to autism, often referring to a 1998 study of 12 children, published in the Lancet, which suggested that the measles, mumps, and rubella (MMR) vaccine predisposed youth to developmental disorders.

The Lancet retracted the paper in 2010 and subsequent studies have failed to find a causal link.
"Time and time again researchers have tried to substantiate this idea that there is a link between autism and vaccines but they have not been able to," said Theodore Tomeny, autism researcher with University of Alabama in the US.
"Unfortunately the idea is still very much out there, being promoted by a vocal minority online. That's problematic because often only one side of the story is being told," Tomeny said.
The researchers note that recent outbreaks of previously eradicated, vaccine-preventable diseases like measles and pertussis have been linked to refusal to vaccinate and anti- immunization-related beliefs.

A few studies have provided clues as to what drives anti-vaccine sentiment, but they have relied on small samples of people.
Between 2010 and 2015, anti-vaccine tweets became, overall, more common nationwide. As the number of households that made over USD 200,000 annually increased or the number of women who had delivered a baby in the past 12 months increased, so did the amount of anti-vaccine tweets in a particular region.
Vargo stressed that he does not see Twitter posts as a representative sample of overall public opinion, but rather a pulse of the level of anti-vaccine activism in an area.

Ultimately, he envisions using the algorithm developed for the study to create real-time maps that pediatricians could use to gauge anti-vaccine sentiment in the communities.