Public Release: 

Dynamics of vaccination

Proceedings of the National Academy of Sciences

A study explores tipping points in vaccination-related behavior during the 2014-2015 Disneyland, California measles outbreak. Social norms, perceived vaccine risk, and perceived disease risk can influence the decision to vaccinate. Chris Bauch and colleagues used artificial intelligence approaches to analyze trends in people's attitudes toward vaccination using measles-related Twitter and Google search data from the United States, including California, before and after the Disneyland measles outbreak. Statistical analyses of social media data suggested that social media users' sentiments toward vaccines exhibit a pattern of increased variability beginning years before the outbreak. The authors suggest that this pattern is characteristic of systems approaching a tipping point, which would induce a different status quo. An accompanying mathematical theory of the complex interactions surrounding vaccination decisions also indicated that the population was approaching a tipping point, following which vaccine uptake would have collapsed and large epidemics would have occurred. However, the Disneyland outbreak likely increased the perceived risk of the disease, moving the population away from the tipping point. The findings point to methods to help identify populations at heightened risk of widespread vaccine refusal, according to the authors.


Article #17-04093: "Critical dynamics in population vaccinating behavior," by A. Demetri Pananos et al.

MEDIA CONTACT: Chris T. Bauch, University of Waterloo, CANADA; tel: 519-888-4567 ex: 32250; e-mail: <>

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