T hanks to vaccines, some illnesses that once ravaged our children are little more than memories.
Immunizations have helped cut U.S. cases of polio, whooping cough, tetanus and diphtheria up to 99 percent. The viruses and bacteria that cause them still exist in this country or in developing nations just a plane ride away. Without vaccines, those diseases could return. Before the measles vaccine, for instance, nearly everyone in the United States got measles. Easily spread, measles caused more than half a million illnesses and 400 deaths a year.