Public health officials turned to the courts to intervene. First, they got a court order to examine the churches’ children in their homes, then to admit children to the hospital for medical care. Finally, they did something that had never been done before or since: They got a court order to vaccinate children against their parents’ will. Children were briefly made wards of the state, vaccinated and returned to their parents. At the time, a religious exemption to vaccination had been on the books in Pennsylvania for about a decade.

To prevent doctors from violating his church’s beliefs against vaccination, the pastor of the Faith Tabernacle Church asked the American Civil Liberties Union to represent him. It refused. “There is certainly a free exercise of religion claim by the parents,” said Deborah Leavy, the executive director of the A.C.L.U. of Pennsylvania, “but there is also a competing claim that parents don’t have the right to martyr their children.”

When spring came and the epidemic faded, C.D.C. officials published the results of their investigation. Over a third of those infected — 486 of 1,424 — belonged to one of those two churches, as did six of the nine dead children.

At the Children’s Hospital of Philadelphia, we saw more than 200 children in our emergency department and admitted about 40. Children would come in, covered in rashes, squinting in the bright light (a side effect caused by eye irritation), struggling to breathe and often extremely dehydrated. It was like being in a war zone. When I asked their parents why they had done what they had done, they all had the same answer: “Jesus was my doctor.”

It seems to me that if religion teaches us anything, it’s to care about our children, to keep them safe. Independent of whether one believes in Jesus, or that the four Gospels are an accurate account of what he said and did, you have to be impressed by the figure described. At the time of Jesus, around 4 B.C. to 30 A.D., child abuse was the “crying vice” of the Roman Empire. Infanticide and abandonment were common. Children were property, no different from slaves. But Jesus stood up for children. In Matthew 25:40, he said, “Verily, I say unto you, Inasmuch as ye have done it unto one of the least of my brethren ye have done it unto me” — a quote that could be emblazoned onto the entranceway of every children’s hospital in the world.