Quantifying the Impact of Misinformation and Vaccine-Skeptical Content on Facebook
Join the Cyber Policy Center on January 21 from 1PM–2PM Pacific for a seminar with Jennifer Allen, moderated by Jeff Hancock. Stanford affiliates are invited to join us at 12:40 PM for lunch, prior to the seminar.
Low uptake of the COVID-19 vaccine in the US has been widely attributed to social media misinformation. To evaluate this claim, we introduce a framework combining lab experiments (total N = 18,725), crowdsourcing, and machine learning to estimate the causal effect of 13,206 vaccine-related URLs on the vaccination intentions of US Facebook users (N ≈ 233 million). We estimate that the impact of unflagged content that nonetheless encouraged vaccine skepticism was 46-fold greater than that of misinformation flagged by fact-checkers. Although misinformation reduced predicted vaccination intentions significantly more than unflagged vaccine content when viewed, Facebook users’ exposure to flagged content was limited. In contrast, mainstream media stories highlighting rare deaths after vaccination were not flagged by fact-checkers, but were among Facebook’s most-viewed stories. Our work emphasizes the need to scrutinize factually accurate but potentially misleading content in addition to outright falsehoods. Additionally, we show that fact-checking has only limited efficacy in preventing misinformed decision-making and introduce a novel methodology incorporating crowdsourcing and machine learning to better identify misinforming content at scale.
About the Speaker
Jenny is a postdoctoral researcher in the Computational Social Science Lab at the University of Pennsylvania. In Fall 2025, she will join NYU Stern as an Assistant Professor of Technology, Operations, and Statistics and a core faculty member of the Center for Social Media and Politics. She received her PhD in Management Science from MIT in 2025 and previously worked at Meta and Microsoft Research. Her research interests include misinformation, political persuasion, and the wisdom of crowds.