It was like a horror movie. The invisible polio virus would strike, leaving young children on crutches, in wheelchairs or in a dreaded “iron lung[1]” ventilator. Each summer, the fear was so great that public pools and movie theaters closed[2]. Parents canceled birthday parties[3], afraid their child might be the next victim. A U.S. president paralyzed by polio called for Americans to send dimes to the White House[4] to...