But most vaccine skepticism, if by that we mean reluctance, is not based on conspiracy theorizing — it’s based on risk-benefit calculations. You may think it’s an innumerate calculation. But when you look at patterns of uptake in the United States, two factors stand out, factors that are larger in their effect than partisanship: age and density. The older you are and the denser your community, the more likely you are to be vaccinated. The younger you are, and the more rural your community, the less likely you are to have gotten it. This reflects the real facts about the...