(RNN) – It's not just politics Russians have been meddling in.
Researchers from George Washington University have published a study indicating that Russian trolls have also muddied the online discourse surrounding vaccines.
The paper, "Weaponized Health Communication: Twitter Bots and Russian Trolls Amplify the Vaccine Debate" was released online on Thursday. It will later appear in the American Journal of Public Health.
In it, the researchers found that "Russian trolls promoted discord" on the vaccine issue. They found that bots, meanwhile, "spread malware and … disseminated antivaccine messages."
"Accounts masquerading as legitimate users create false equivalency, eroding public consensus on vaccination," they write.
A significant anti-vaccine movement claims to varying degrees that the chemicals in vaccines or the frequency with which they are administered can cause autism or other developmental problems in children.
Medical science refutes this. The Centers for Disease Control and Prevention's unambiguous position is that "there is no link between vaccines and autism."
Nonetheless, debate rages online, particularly on social media platforms like Facebook and Twitter.
A University of Alabama study found that between 2009 and 2015, about half of all tweets about vaccines were negative.
"We found that anti-vaccine sentiment seems to be prevalent on Twitter," Theodore Tomeny, a University of Alabama professor, told NBC News last year.
According to this latest study, Russian trolls and bots have now taken to amplifying that sentiment.
"Although it's impossible to know exactly how many tweets were generated by bots and trolls, our findings suggest that a significant portion of the online discourse about vaccines may be generated by malicious actors with a range of hidden agendas," David Broniatowski, who helped conduct the study, told The Guardian.
The study found that the accounts also sometimes took pro-vaccination positions, using inflammatory rhetoric to stoke the divisions of both groups.
"Let them die from measles, I'm for #vaccination!" one tweet read, The Guardian reported.
"These trolls seem to be using vaccination as a wedge issue, promoting discord in American society," Mark Dredze, another member of the team that conducted the study, told the paper.
The researches examined a sample of 1.7 million tweets written between July 2014 and Sept. 2017, according to The Guardian.
They found that bots and trolls tweeted far more frequently – 22 times more often - about vaccines, specifically, than humans.
While attention on Russian meddling has focused on activity around the 2016 presidential election, trolls look to exploit other contentious issues in America such as gun control and racial division.
"What Russia seems to want is divisiveness everywhere else, and they try to get a competitive advantage by destabilizing every country around them," Republican Sen. James Lankford of Oklahoma told NPR earlier this year. "They've done it for years, and they've finally come here."
Anti-vaccination activism can have real-world impact.
A 2016 study published in JAMA: The Journal of the American Medical Association concluded that "a substantial proportion of the US measles cases in the era after elimination were intentionally unvaccinated."
Europe is currently dealing with a major measles outbreak, infecting more than 41,000 people this year. That's already almost double last year's entire total and about eight times as many as all of 2016, according to the BBC.
"The majority of cases we are seeing are in teenagers and young adults who missed out on their MMR (mumps-measles-rubella) vaccine when they were children," Dr. Mary Ramsay, an English public health official, told the BBC.
A small measles outbreak also hit the US this year.
The George Washington researchers found it will be difficult to combat anti-vaccine sentiment, though.
"Directly confronting vaccine skeptics enables bots to legitimize the vaccine debate," they wrote. "More research is needed to determine how best to combat bot-driven content."