Cold War tensions and the polio vaccine polio vaccine. By the 1950, Jonas Salk had tested both live, attenuated polio vaccines and formaldehyde killed polio vaccines in monkeys and by 1952, began testing on humans. The killed vaccine was found to be effective, with proper filtration of the biological culture. A problem with this vaccine was the perception that to be adequately protected; a child had to get three Salk shots, properly spaced, and a recommended booster shot once a year, which was expensive. It should be noted however, that Jonas Salk, himself, has stated in interviews that this perception is not at all true. This vaccine
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,