Polio is a virus that multiplies in the intestines and can quietly spread from person to person. In some children, it invades the nervous system and paralyzes the legs or lungs. In the 1950s, outbreaks struck every summer in the United States, filling hospitals with children in iron lungs. The inactivated polio vaccine ended that fear. With just four doses, children are protected for life. The United States has been polio-free since 1979, and vaccination has prevented more than 24 million cases of paralysis worldwide since 1988.

Links