Ken Haller is 64, but he vividly remembers having measles when he was 7. And mumps when he was 10. And chickenpox when he was 11, which required him to keep socks on his hands so he wouldn’t gouge his skin from scratching. He still has a faint scar on his nose from one pustule he scratched too intensely. Haller is also a pediatrician who has treated babies who developed meningitis from Haemophilus influenzae (now vaccine-preventable) and became blind—or died.