The American anti-vaccination movement received some unlikely help in pushing its messages, a new report finds.

A study from George Washington University found that Russian trolls were active in pushing anti-vaccination messages — as well as pro-vaccination messages.

“Compared with average users, Russian trolls, sophisticated bots, and ‘content polluters’ tweeted about vaccination at higher rates,” the study found. “Whereas content polluters posted more anti-vaccine content, Russian trolls amplified both sides.”

That would fit the strategy that the Russian government is accused of using in the 2016 U.S. presidential election and the lead-up to it, with Russian trolls amplifying both sides of divisive social issues, especially related to race. The study warned that the Russian messages on anti-vaccination were meant to chip away at public confidence over the effectiveness of vaccinations, The Daily Dot reported.

Though anti-vaccination voices have always existed, the debate has grown sharper amid a series of outbreaks of measles and other ailments once kept in check by vaccines. This has led to debates over whether parents should be allowed to opt out of school-required vaccinations.

In Colorado, state lawmakers have weighed legislation that would make it more difficult to opt out of vaccine requirements. The bill would require parents who don’t want to vaccinate their children for religious or personal purposes to apply in person at a state office, the Associated Press reported.

Critics have pointed out that the anti-vaccination movement is fueled by misinformation about the effectiveness and dangers of vaccines.

Russian trolls fueled anti-vaccination debate in U.S. by spreading misinformation on Twitter https://t.co/Moq4Nf2B1h pic.twitter.com/ejdm9zECap — CBS News (@CBSNews) May 31, 2019

The report on the involvement of Russian trolls in the vaccination debate comes as many cybersecurity experts warn that Russia has continued to push the scales in American politics. As The New York Times reported, the FBI warned that Russia would once again be meddling in the election and called it a “significant counterintelligence threat.”

FBI Director Christopher Wray said they had already tracked Russian interference in the 2018 midterm elections and believed that it would continue in 2020.

“We recognize that our adversaries are going to keep adapting and upping their game,” Wray said. “So we are very much viewing 2018 as just kind of a dress rehearsal for the big show in 2020.”

This comes just days after Donald Trump admitted (for the first time) in a tweet that Russian interference helped him to win the 2016 presidential election. Trump had been hesitant to point the finger at Russia, even siding with Russian President Vladimir Putin when he denied that Russia played any role in interfering in the election.