On April 12, in an auditorium at the University of Michigan, “amid fanfare and drama far more typical of a Hollywood premiere than a medical meeting” (according to The New York Times), Dr. Thomas Francis announced the results of an investigation into the polio vaccine developed by a former student of his, Dr. Jonas Salk. The verdict: Salk’s vaccine worked. The 150 journalists in the audience rushed off to file their stories, and, by the next morning, thousands of doses of vaccine were on their way to children across America. Just as quickly, Salk was on his way to becoming a scientific celebrity.

The announcement did not come as a surprise. Early results from clinical trials had been promising, leading drug manufacturers to prepare for production more than a year ahead of time. By the date of the announcement (the tenth anniversary of the death of President Franklin D. Roosevelt, a polio patient), 27 million doses had been stockpiled in warehouses around the country.

Many adults still remembered the great epidemic of 1916, which killed more than 6000 and left another 27,000 paralyzed. As recently as 1952 more than 3000 had died of polio, and more than 20,000 had been fully or partially paralyzed. These memories made the public’s fear of polio so great that shortages of the vaccine developed despite the advance preparation.

Even worse, in May, it became apparent that one manufacturer had not properly killed the viruses in its vaccine. Thousands of children were inadvertently given live doses, and 260 of them developed the disease. The laboratory at fault was quickly isolated, the public was reassured, and the vaccination program continued.

Newspapers and politicians hailed Salk as a hero, but some scientists saw him as more of a self-promoting credit hog. Among the biggest critics was Dr. Albert Sabin, who was developing a vaccine based on live viruses that were weakened rather than killed. The Sabin vaccine was swallowed instead of being injected, making it much easier to administer and, he claimed, more effective. Sabin’s vaccine was introduced in the early 1960s, and quickly displaced the Salk version.

Between them, the Salk and Sabin vaccines made striking progress. By the mid-1960s, the annual total of new polio cases in the United States was often less than 100, and by the early 1990s, it had been completely eradicated. Global cases are now down to less than 1500, concentrated in a handful of countries, and, by the end of the decade, the World Health Organization hopes to enter the cessation phase of its polio eradication campaign.