On Apr. 25, 1954 the Vaccine Advisory Committee of the National Foundation for Infantile Paralysis recommended a large-scale national trial of Salk’s vaccine based on a report involving more than 9,000 who had been inoculated in pilot trials since May 16, 1953.

National testing began on one million children, ages six to nine, who became known as the Polio Pioneers: half received the vaccine, and half received a placebo. One-third of the children, who lived in areas where vaccine was not available, were observed to evaluate the background level of polio in this age group.