Tanushree Mitra wrote a computational paper on this in 2016 [1], finding something similar:
"Using four years of longitudinal data capturing vaccine discussions on Twitter, we identify users who persistently hold pro- and anti-attitudes, and those who newly adopt anti-attitudes towards vaccination. After gathering each user's entire Twitter timeline, totaling over 3 million tweets, we explore differences in the individual narratives across the user cohorts. We find that those with long-term anti-vaccination attitudes manifest conspiratorial thinking, mistrust in government, and are resolute and in-group focused in language."
"Using four years of longitudinal data capturing vaccine discussions on Twitter, we identify users who persistently hold pro- and anti-attitudes, and those who newly adopt anti-attitudes towards vaccination. After gathering each user's entire Twitter timeline, totaling over 3 million tweets, we explore differences in the individual narratives across the user cohorts. We find that those with long-term anti-vaccination attitudes manifest conspiratorial thinking, mistrust in government, and are resolute and in-group focused in language."
[1] http://comp.social.gatech.edu/papers/icwsm16.vaccine.mitra.p...