April 12, 1955, the results of the largest clinical trial of a vaccine in history were announced: Jonas Salk’s polio vaccine was found safe, effective and potent. The American government licensed the vaccine for use that afternoon, the same day that the trial results were announced. “Polio season” typically began in May and ran through the rest of the summer, so the vaccine was approved just in time.
The approval of the polio vaccine resulted in a nationwide celebration, with children being let of out of school. In 1952 half of the cases of polio in the United States resulted in paralysis so it was a huge relief to have effective protection against the disease.
The safety trials of the vaccine began in May 1953 and consisted of 5300 individuals, including Salk, his wife and his three sons. The field trial began in June 1953 with 1.8 million students from grades 1-3 and over 250,000 volunteers. In 2014 there were fewer than 500 cases of polio globally.
Vaccine research and polio eradication has certainly come a long way in 60 years!