On Apr. 12, 2005 marked the 50th anniversary of the announcement that the polio vaccine, developed by Jonas Salk and his team of scientists at the University of Pittsburgh, worked.

“Safe, effective, and potent” were the words used to announce to the world that an effective vaccine had been found against a disease that once paralyzed 13,000–20,000 persons each year in the United States.

In 1979, fewer than 25 years after introduction of the vaccine, the last indigenously acquired case of polio caused by wild poliovirus was detected in the United States; 15 years later, in 1994, the Western Hemisphere was certified polio-free.