The breakthrough vaccine developed by Jonas Salk is the polio vaccine, which was introduced in 1955. Polio, or poliomyelitis, is a viral infectious disease that primarily affects children and can lead to paralysis and even death. Salk's vaccine was made using a killed version of the virus, making it safe for use. The widespread administration of the polio vaccine significantly reduced the incidence of the disease in the United States and around the world. Salk's work earned him worldwide recognition and is credited with saving countless lives and preventing disability caused by polio.