Internet trolls and bots directed by the Russian government spread online information intended to sow discord in the US over the legitimacy and effectiveness of vaccines, according to multiple media outlets.

According to researchers, Russian trolls played from both sides, tweeting pro- and anti-vaccine content. “These trolls seem to be using vaccination as a wedge issue, promoting discord in American society,” Mark Dredze, a team member and professor of computer science at Johns Hopkins, which was involved in the study, told the Guardian.

In tweeting both pro- and anti-vaccine information, the Russian trolls are able to erode public trust in vaccination across borders. The study was published in the American Journal of Public Health and comes as Europe is facing a major outbreak of measles, which has been partly attributed to falling vaccination rates.