DP18788 Vax Populi: the Social Costs of Online Vaccine Skepticism
This paper quantifies the impact of online vaccine skepticism on pediatric vaccine uptake, vaccine-preventable hospitalizations, and their related costs. We propose an instrumental variable strategy that leverages the complex structure of social networks. By matching Italian vaccine-related tweets for 2013-2018 with vaccine coverage and preventable hospitalizations data, we find that a 10pp increase in anti-vaccine sentiment causes a 0.43pp decrease in Measles-Mumps-Rubella vaccine coverage. This shift results in an additional 2.1 hospitalizations per 100,000 residents and an 11% increase in relevant healthcare expenses. Conversely, we find no statistically significant impact on vaccines not targeted by online misinformation (e.g., Hexavalent, Meningococcal, Pneumococcal). The results of a simulated model further suggest that informative campaigns are the most effective method to mitigate the effects of online misinformation and reduce polarization.
