Pertussis, or whooping cough, was almost unknown in America 40 years ago.
Cases in 1976 numbered barely over a thousand. But in the years since vaccine resistance grew, so did cases of pertussis, up to nearly 50,000 just five years ago.
A new study of outbreaks and vaccine resistance show them in close proximity physically. Harvard University immunologist Barry Bloom is one of the authors of the study, and our guest.