Polio vaccine 900 developed polio; in the group receiving the vaccine, only one out of 7,500 developed polio, making the vaccine 88% effective during the first year. However, other researchers believed that the one case was likely caused by the vaccine, and two more possible cases were reported later. After this meeting, Brodie, whose polio vaccine was at least partially effective and reasonably safe, and who developed several ground-breaking ideas about vaccination whose validity was confirmed two decades later with the development of the Salk vaccine, was immediately fired and had trouble finding employment again. Brodie died three and a half years
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,