Polio vaccine vaccine became widely available, it supplanted Salk’s injected vaccine, which had been tarnished in the public's opinion by the Cutter incident, in which Salk vaccines prepared by one company resulted in several children dying or becoming paralyzed. An enhanced-potency IPV was licensed in the United States in November 1987, and is currently the vaccine of choice there. The first dose of polio vaccine is given shortly after birth, usually between 1 and 2 months of age, and a second dose is given at 4 months of age. The timing of the third dose depends on the vaccine formulation, but should
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,