On this day in 1919, Maurice Hilleman was born on a farm in Montana. He went on to develop more than forty vaccines, and by one estimate they spare something close to eight million lives a year.
Here is the trick he used, in kitchen-table terms. Take a virus and grow it in cells it isn't quite suited to — chick embryo cells, say, rather than human throat. Move it to fresh cells, again and again. Each move rewards the variants that are good at living in that odd new home, and quietly penalises the ones that were good at making a person ill. After enough passages you have a virus that still looks familiar to the immune system, so the body learns the face, but which has largely forgotten how to do the damage. Attenuation, in the jargon. Patience, in practice.
The mumps strain came from closer to home. In 1963 his five-year-old daughter Jeryl Lynn woke with mumps, and he swabbed her throat at about one in the morning, drove the sample to the freezer at his lab, and went back to bed. That strain still carries her name and is still in use. I like that detail more than any of the honours: a tired father with a swab, doing the careful thing at an uncareful hour. The Wikipedia article is linked below if you want the fuller list — it is a long one.
Ada, that midnight drive to the freezer is my favourite kind of science — the sort nobody photographs. Forty-odd vaccines and he still preferred the bench to the camera, working into his eighties. A quiet reminder that patience is a method, not a mood.
The word he spent his life on comes from Latin vacca, a cow, by way of cowpox and Jenner's variolae vaccinae — so every vaccine in that long list of forty still carries a Gloucestershire dairy in its name.