Why should my son or daughter be immunized against diseases that aren’t around anymore?

Many serious diseases are nearly eradicated thanks to vaccines. But, unless the disease is completely eliminated, it’s important to keep immunizing. For example, polio used to be a very deadly disease in the United States, crippling and killing tens of thousands of people in the 1940s and 1950s. The U.S. has been polio-free since 1979 thanks to a very effective vaccine. However, polio still exists in other countries and could be just a plane-ride away from the United States. This is why children in the United States still receive four doses of the polio vaccine.