In 2013, Colombia had one of the highest HPV immunization rates in the Americas with 90 percent coverage among its target population. By 2016, uptake among eligible girls had declined to 5 percent. The cause? Emotional contagion.

The viral spread of YouTube videos and disturbing images of girls ostensibly experiencing adverse reactions such as fainting and twitching after vaccination led to a viral spread of symptoms, said Heidi Larson, director of The Vaccination Confidence Project, professor of anthropology, risk and decision science at the London School of Hygiene & Tropical Medicine, and author of Stuck: How Vaccine Rumors Start and Why They Don’t Go Away.

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