Sarah Stewart (cancer researcher) at the age of 39. Stewart returned to the NIH in 1951, joining the National Cancer Institute (NCI), and eventually becoming medical director. Stewart developed an interest in researching viral links to cancer in light of the pioneering research of Jonas Salk in developing a vaccine for the virus which caused polio. Stewart developed an interest in researching viral links to cancer in light of the pioneering research of Jonas Salk in developing a vaccine for the virus which caused polio. Stewart is credited with discovering the Polyomavirus in 1953. She and research partner, Dr. Bernice E. Eddy, were successful
Jonas Salk assembled, devoted himself to this work for the next seven years. The field trial set up to test the Salk vaccine was, according to O'Neill, "the most elaborate program of its kind in history, involving 20,000 physicians and public health officers, 64,000 school personnel, and 220,000 volunteers." Over 1,800,000 school children took part in the trial. When news of the vaccine's success was made public on April 12, 1955, Salk was hailed as a "miracle worker" and the day almost became a national holiday. Around the world, an immediate rush to vaccinate began, with countries including Canada, Sweden, Denmark, Norway,