My article for the Telegraph: In 1934, in their spare time, two American biologists, Pearl Kendrick and Grace Eldering, developed a vaccine for whooping cough, then the biggest killer of children in the United States.
Within four years their vaccine was being used throughout Michigan and within six it was being used nationwide. Whooping cough rapidly retreated.
Since then there have been spectacular advances in biology, including the identification of the genetic material, the ability to read its code, an understanding of the structure of viruses and the proteins from which they are made, plus knowledge of how immunity works.
Read more on rationaloptimist.com