So many years have passed since I first learned about this subject that when I began to write this piece I wondered if the thinking in the field had changed in the intervening decades. Had new research shown the old findings about maternal antibodies in humans to be incorrect? To be sure that my understanding wasn't out of date, I burrowed into the library stacks (I'm not complaining—it's a favorite place). By the time I was done, I had read or scanned more than 2,000 abstracts and papers. And, no, the thinking about human infant immunity hasn't changed at all. Instead, an awful lot of the old work has been forgotten, and there is not much new research.