Anti-vaxxers tend to congregate in urban centers, creating anti-vaccination hotspots in cities like Seattle, Portland, Phoenix, Salt Lake City, Houston and Kansas City.
This has been true throughout history. In the 19th century, when the smallpox epidemic was raging across the country, anti-vaccination movements sprang up amongst the educated middle class in cities like Boston and Minneapolis.
It seems counterintuitive. We’d like to think that, along with an education, you gain an understanding of how vaccines work — or, at least, a certain respect for the medical experts who are recommending them. And polls have indeed shown that anti-vaccine views are inversely correlated with education levels.