In the midst of today’s harsh debate between anti-vaxxers and those who side with mainstream science, it can be hard to imagine a time when Americans almost universally embraced vaccination.

That time was the 1950s, when the very real, devastating effects of polio overshadowed any questions of vaccine safety. In 1952, the worst polio outbreak in American history infected 58,000 people, killing more than 3,000 and paralyzing 21,000 — the majority of them children. As Time reported, “Public swimming pools were deserted for fear of contagion. And year after year polio delivered thousands of people into hospitals and wheelchairs, or into the nightmarish canisters called iron lungs.”

Dr. Jonas Salk discovered the polio vaccine. When the first mass inoculations against polio were held in 1954, most parents feared that it wouldn’t become widely available fast enough to save their kids.

Salk had already tested his vaccine on volunteers — starting with himself, his wife, and their children — who’d successfully produced polio antibodies without getting sick. By June, nearly two million schoolchildren in 44 states had been inoculated, and a year later the vaccine was officially licensed.

During its initial testing, the biggest safety question about Salk’s vaccine centered on the potential danger of injecting humans with monkey tissue. To make his vaccine, Salk’s team harvested kidneys from live monkeys and injected them with live polio virus, which quickly multiplied in the kidney cells. Then the team used formaldehyde to kill the virus before injecting it into humans.

Salk claimed that the traces of monkey kidney present in each dose of the vaccine were so tiny that they posed no health risks.

Indeed, the greatest safety threat came not from monkeys but from human error: One of the labs licensed to produce the vaccine accidentally contaminated a batch with live polio virus in 1955. That batch killed five people and paralyzed 51.

The vaccine continues to be a lifesaver. Within the first few years, it cut polio cases in the U.S. by half. By the time of Salk’s death in 1995, polio was virtually extinct in the U.S. and falling worldwide.

Source: The Vaccine Everyone Wanted
© 2017 Time Inc. All Rights Reserved.