Vaccines have become a victim of their own success.  In 1809 Massachusetts became the first state to pass a law requiring a vaccination – of smallpox – ushering a series of public health victories over a number of serious diseases.  In the past 200 years smallpox has been eradicated, and measles, polio, rubella and tetanus have become so rare that they have disappeared from public consciousness. The number of children who contract vaccine-preventable diseases today is tiny compared to the numbe...