Polio (or Poliomyelitis) is an infectious viral disease that attacks nerve cells and, sometimes, the central nervous system. Its initial symptoms are much like the flu, but the disease then progresses, causing muscles to waste away. It can lead to paralysis and even death. It had been an incurable disease since ancient time, but at the height of its devastation in American, Dr. Jonas Salk discovered a vaccine. It was 1952. Two years later, on February 23, 1954, he Dr. Salk conducted his large field trial, inoculating 423,000 second-grade children in Pittsburgh, where he was head of the Virus Research Lab at the University of Pittsburgh. The results were amazing: 60-70% prevention.
Unfortunately, Salk vaccinations were stopped when it was found to have caused about 200 cases of polio, claiming 11 lives. Officials, though, discovered that the disease-causing vaccine all came from one poorly-made batch. By 1959, 90 other nations were using the Salk vaccine. The World Health Organization has a goal to completely eradicate polio during the first decade of the 21st century.