The compelling story of vaccination. We may fear terrorist attacks, but in truth humans have always had far more to fear from infections. In 1919, Spanish flu killed over 50 million people, more than died in both world wars combined. In 1950, an estimated 50 million people caught smallpox worldwide, of whom 10 million died. In 1980, before measles vaccine was widely used, an estimated 2.6 million children died of measles every...