In April 1954, a group of first graders lined up in the gymnasium of an elementary school in McLean, Virginia for the start of the Salk polio vaccine trials. In an era before widespread federal government involvement in public health, the National Institute of Infantile Paralysis executed an unprecedented experiment involving nearly 2 million children and tens of thousands of doctors, nurses, and volunteers. It was the largest peacetime mobilization in American history.

While scientists evaluated the results, Americans waited anxiously to find out whether the vaccine was safe and effective, putting an end to 40 years of fear. But in the spring of 1955, a shocking revelation would bring the vaccination program to a sudden halt.

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