As measles cases have surged across the US and Europe this year, there’s been a lot of talk about what’s causing the outbreaks. Among the most discussed issues: mistrust of the medical establishment, populist politics fueling vaccine doubt, and the spread of misinformation on social media. A comprehensive survey found that people in higher-income countries were among the least confident in vaccine safety — particularly in North America and Europe. Meanwhile, vaccine trust was highest in countries where preventable diseases still spread, such as Bangladesh and Rwanda. So the further people are from outbreaks, and the more distant the memory of diseases like whooping cough and measles, the more likely they are to shun vaccines. Julia Belluz writes in Vox that the survey also uncovered something that unites some of the communities where outbreaks have been spreading lately, and it’s not as easy to talk about: religious belief.