Seventy years ago, on April 12, 1955, the United States heard the words: “The vaccine works.” That moment marked the official debut of the polio vaccine, developed by Dr. Jonas Salk. At the time, Americans feared polio almost as much as nuclear war. Each summer brought panic as outbreaks closed pools, theaters, and playgrounds. But with one medical breakthrough, a decades-long crisis began to end. Today, as measles cases rise and vaccine hesitancy grabs headlines, the story of the polio vaccine reminds us of the power science can have in saving lives.
The Fear That Gripped a Nation
For much of the early 20th century, polio was a parent’s worst fear. The virus often struck without warning. It could cause permanent paralysis or death. A 1916 outbreak in the U.S. left 27,000 people paralyzed and killed 6,000. In the 1950s, a survey revealed that Americans feared only nuclear war more than polio.
Summer brought the highest risk. Local outbreaks often led to the closure of public places to try and slow the spread. Parents kept children indoors. The disease hit mostly young kids, creating widespread fear and heartbreak.
A Young Scientist With a Bold Idea
In 1947, Jonas Salk, a 33-year-old researcher, took over a virology lab at the University of Pittsburgh. He believed the best way to stop polio was with a “killed-virus” vaccine—one that used a virus treated so it could no longer reproduce, but still trained the immune system.
At the time, many experts disagreed. Most believed a live-virus vaccine, which used a weakened form of the virus, would be stronger and last longer. One of those experts was Albert Sabin, an older, well-known researcher at Cincinnati Children’s Hospital.
Sabin was not shy about criticizing Salk. At a 1948 conference, Sabin even mocked Salk in public. Salk later said it felt “like being kicked in the teeth.” Despite this, Salk continued his work.
The First Human Trials
To make the vaccine, Salk used formaldehyde to kill the virus in lab cultures. It was a careful balance. Too much would make the vaccine ineffective. Too little could leave active virus behind.
Once Salk believed it was safe, he and his team tested it on themselves. Then, with permission from parents and institutions, they began testing on children at the D.T. Watson Home for Crippled Children and the Polk State School.
Salk later said he barely slept during those early trials. But the results were promising—the children developed strong antibodies against the virus.
The Largest Vaccine Trial in U.S. History
In 1954, a national trial began. It included 1.8 million children in 44 U.S. states and parts of Canada. Over 600,000 children received the actual vaccine. Others were given placebos.
Public opinion was split. Some parents welcomed the chance to protect their kids. Others were wary. One radio host, Walter Winchell, even warned that the vaccine “may be a killer.”
On April 12, 1955, at the University of Michigan, researchers announced the findings: the vaccine was safe and 80–90% effective. News spread fast. Across the country, people celebrated. Many remembered where they were when they heard.
A Public Good, Not a Private Profit
Despite the historic success, Jonas Salk chose not to patent his vaccine. He believed it belonged to the people. “Could you patent the sun?” he asked in an interview.
Salk’s decision allowed the vaccine to be made widely available. Millions of children were protected in the years that followed. Rates of polio dropped fast in the U.S. and around the world.
Sabin’s Version Takes Over—Then Salk’s Returns
In 1961, Albert Sabin introduced an oral polio vaccine made from a live, weakened virus. It was easier to give, and only needed one dose. By the 1960s, Sabin’s version became the standard across the U.S.
But in 2000, the Centers for Disease Control and Prevention (CDC) returned to recommending Salk’s original inactivated vaccine. The goal was to fully eliminate the small risk of infection linked to the live-virus version and push toward global eradication.
The Legacy of the Polio Vaccine
Thanks to the work of both Salk and Sabin, polio has been nearly wiped out in many parts of the world. Their rivalry pushed science forward. Their vaccines saved millions of lives and ended a public health crisis that once paralyzed a nation with fear.
Today, with new vaccine debates in the spotlight, the 70th anniversary of the polio vaccine is a reminder of what’s possible when science, courage, and public trust come together.
