Salk Polio Vaccine Declared Safe and Effective

On April 12, 1955, results of the largest clinical trial in history were announced: Jonas Salk's inactivated polio vaccine had proved safe, effective, and potent. The trial enrolled 1.8 million children across the United States, Canada, and Finland. The 1952 US polio epidemic had paralyzed over 21,000 people and killed more than 3,000. Salk refused to patent the vaccine, famously asking who could patent the sun. Albert Sabin's oral vaccine followed in 1961. Together they drove a global eradication campaign that reduced polio cases by over 99% worldwide.