Can we predict who might become an active anti-vaxxer?

What causes someone to suddenly embrace conspiracy theories? A new study suggests that people who express distrust in governments on social media are much more likely to embrace irrational beliefs such as anti-vaccination attitudes.

Mitra, Counts, & Pennebaker (2016) analysed more than three million tweets of pro-vaccination and anti-vaccination twitter users, and particularly those that suddenly became anti-vaccination proponents between 1 January 2012 and 30 June 2015. By looking at 850,000 tweets from people who became anti-vaccination proponents the researchers found similarities in the language and topics they used before they started tweeting about vaccinations.

In particular they found these ‘anti-vaccination joiners’ to have strong beliefs in conspiracies and their world-views are conducive to believing in conspiracies about vaccinations.

In fact they had significantly higher mentions of vaccine fraud and chronic health concerns after their first mention of vaccination. This suggests an important characteristic of people holding unfavorable attitude towards vaccination: an inclination towards conspiracy thinking – a way of interpreting the world where conspiracy plays a dominant role (Mitra, Counts, & Pennebaker, 2016, p. 275).

The study also found that anti-vaccination proponents also had much more certainty in their views than pro-vaccination proponents, which is frustrating given the overwhelming scientific evidence supports the safety and effectiveness of vaccinations.


Sun Tzu said "If you know the enemy and know yourself, you need not fear the result of a hundred battles." Unfortunately we know a lot about the effectiveness of vaccines in preventing transmissible diseases, but very little about those that campaign against them. However researchers are worried that many lives will be lost because anti-vaxxers are using websites and social media to persuade people not to vaccinate their children (Kata, 2010; Lee, Whetten, Omer, Pan, & Salmon, 2016).

This study helps to identify the type of person who is likely to become an anti-vaccination proponent – a person who is likely to distrust government and hold entrenched world-views that support conspiracy theories. Unfortunately once a person holds these sorts of conspiratorial world views it is very difficult to reverse them - even when presented with irrefutable scientific facts (Lewandowsky S, Gignac GE, Oberauer K, 2012). It suggests that preventing a person from developing unhealthy world views is the only way to prevent people from believing conspiracy theories about vaccinations.

For individuals with anti-vaccine attitudes, a paranoid world of conspiracy theories, secret, sinister organizations and manipulative government bodies causing harm are all part of their coherent system of beliefs (Mitra, Counts, & Pennebaker, 2016, p. 276).


  • Mitra, T., Counts, S., & Pennebaker, J. (2016). Understanding Anti-Vaccination Attitudes in Social Media. International AAAI Conference on Web and Social Media (pp. 269-278). Cologne: Association for the Advancement of Artificial Intelligence.

  • Lee, C., Whetten, K., Omer, S., Pan, W., & Salmon, D. (2016). Hurdles to herd immunity: Distrust of government and vaccine refusal in the US, 2002–2003. Vaccine.

  • Lewandowsky S, Gignac GE, Oberauer K (2013) The Role of Conspiracist Ideation and Worldviews in Predicting Rejection of Science. PLoS ONE 8(10): e75637. doi:10.1371/journal.pone.0075637

  • Kata, A. (2010). A postmodern Pandora’s box: Anti-vaccination misinformation on the Internet. Vaccine, 1709–1716.