As a primary care internist, I spend a lot of time focusing on preventative health. There are all sorts of screening tests—mammograms, colonoscopies, PSA tests—but none of these actually “prevent” disease. They are designed to find disease at an early stage, allowing treatment that, ideally, avoids the more aggressive forms of the disease. The only preventative measures that actually prevent disease are vaccinations. Our world is an immeasurably better place since the advent of vaccines. Yet there is a complicated psychology that hovers like a fog around the idea of vaccination. In this week’s New England Journal of Medicine, I offer my perspective on “The Emotional Epidemiology of HINI Vaccination.” I invite you to read and comment.