It is slightly ironic that vaccinations, the mechanisms that protect our children from the mortal illnesses that once swept them out of their parents’ hands, are now the focus of our fears, while the once-devastating illnesses are themselves seen as somehow reassuring.

But vaccinations have long been a kind of locus of cultural fear, revealing the nature of our fears. Vaccinations, after all, only work if everyone is in it together. You need to have a herd for herd immunity. Our body politic is splintering and fragmenting, and it is reflected in our vaccination rates. To make a herd, you need to believe in the imagined collective: to be concerned not only about yourself, but the others in the polity.

This fear isn’t new, though our particular iteration of it is modern. Although vaccinations were actually folk medicine in their earliest form (farmers knew that milkmaids exposed to cowpox rarely got smallpox), as the writer Eula Biss points out in On Immunity, people have almost always distrusted them. During an 18th-century smallpox epidemic, citizens in France contested their use, leading Voltaire to inveigh that “twenty thousand persons whom the small-pox swept away at Paris in 1723 [c]ould have been alive at this time.”