8 Things You May Not Know About the Polio Vaccine

“Polio was never the raging epidemic portrayed in the media, not even at its height in the 1940s and 1950s,” writes David M. Oshinsky in his Pulitzer Prize-winning book Polio: An American Story. During those decades, 10 times as many children died in accidents and three times as many succumbed to cancer. Oshinsky notes that polio inspired such fear because it struck without warning and researchers were unsure of how it spread from person to person. In the years following World War II, polls found the only thing Americans feared more than polio was nuclear war.

A year after his nomination as a Democratic vice presidential candidate, rising political star Franklin D. Roosevelt contracted polio while vacationing at his summer home on Campobello Island in 1921. The disease left the legs of the 39-year-old future president permanently paralyzed. In 1938, five years after entering the White House, Roosevelt helped to create the National Foundation for Infantile Paralysis, later renamed the March of Dimes Foundation, which became the primary funding source for Salk’s vaccine trials. Employing “poster children” and enlisting the star power of celebrities from Mickey Rooney to Mickey Mouse, the grassroots organization run by Roosevelt’s former Wall Street law partner Basil O’Connor was raising more than $20 million per year by the late 1940s.

While most scientists believed that effective vaccines could only be developed with live viruses, Salk developed a “killed-virus” vaccine by growing samples of the virus and then deactivating them by adding formaldehyde so that they could no longer reproduce. By injecting the benign strains into the bloodstream, the vaccine tricked the immune system into manufacturing protective antibodies without the need to introduce a weakened form of the virus into healthy patients. Many researchers such as Polish-born virologist Albert Sabin, who was developing an oral “live-virus” polio vaccine, called Salk’s approach dangerous. Sabin even belittled Salk as “a mere kitchen chemist.” The hard-charging O’Connor, however, had grown impatient at the time-consuming process of developing a live-virus vaccine and put the resources of the March of Dimes behind Salk.

After successfully inoculating thousands of monkeys, Salk began the risky step of testing the vaccine on humans in 1952. In addition to administering the vaccine to children at two Pittsburgh-area institutions, Salk injected himself, his wife and his three sons in his kitchen after boiling the needles and syringes on his stovetop. Salk announced the success of the initial human tests to a national radio audience on March 26, 1953.

On April 26, 1954, six-year-old Randy Kerr was injected with the Salk vaccine at the Franklin Sherman Elementary School in McLean, Virginia. By the end of June, an unprecedented 1.8 million people, including hundreds of thousands of schoolchildren, joined him in becoming “polio pioneers.” Researchers used the double-blind method, now standard, in which neither the patient nor person administering the inoculation knew if it was a vaccine or placebo. Although no one was certain that the vaccine was perfectly safe—in fact, Sabin argued it would cause more cases of polio than it would prevent—there was no shortage of volunteers.

On April 12, 1955, the day the Salk vaccine was declared “safe, effective and potent,” legendary CBS newsman Edward R. Morrow interviewed its creator and asked who owned the patent. “Well, the people, I would say,” said Salk in light of the millions of charitable donations raised by the March of Dimes that funded the vaccine’s research and field testing. “There is no patent. Could you patent the sun?” Lawyers for the foundation had investigated the possibility of patenting the vaccine but did not pursue it, in part because of Salk’s reluctance.

Just weeks after the Salk vaccine had been declared safe, more than 200 polio cases were traced to lots contaminated with virulent live polio strains manufactured by the Cutter Laboratories in Berkeley, California. Most taken ill became severely paralyzed. Eleven died. In the haste to rush the vaccine to the public, the federal government had not provided proper supervision of the major drug companies contracted by the March of Dimes to produce 9 million doses of vaccine for 1955. Although the United States surgeon general ordered all inoculations temporarily halted, Americans continued to vaccinate themselves and their children. Outside of the “Cutter Incident,” not a single case of polio attributed to the Salk vaccine was ever contracted in the United States.

Once Sabin’s oral vaccine finally became available in 1962, it quickly supplanted Salk’s injected vaccine because it was cheaper to produce and easier to administer. Ultimately, both vaccines produced by the bitter rivals nearly eradicated the disease from the planet. According to the World Health Organization (WHO), there were only 416 reported cases of polio worldwide in 2013, mostly confined to a handful of Asian and African countries. In 2023, there were 6. The WHO has urged polio-free countries to return to Salk’s killed-virus vaccine.