LAUSR

Although vaccine misinformation has been a longstanding problem, the growth of social media and divides based on political ideology have raised novel concerns. One noteworthy example involves the Russian Internet Research Agency's deployment of operatives on Twitter (i.e., trolls) working to sow discord among the American public. We examine 1,959 tweets made by trolls between 2015 and 2017 about vaccination to better understand their efforts to spread vaccine misinformation. Our results indicate that misinformation was more likely to be perpetuated by left and right trolls than nonpartisan trolls. There was, however, relatively little user engagement with vaccine tweets containing misinformation and no differences in engagement with misinformation shared by partisan and nonpartisan trolls. Trends in the psycholinguistic properties of language in trolls' vaccine tweets suggest that right and left trolls were more likely to include cognitive process words (i.e., insight, causation, discrepancy, certainty, differentiation, and tentativeness) than were nonpartisan trolls.