Jonas Salk

Although no one was safe from polio, the virus mostly affected kids. Most infected people showed no symptoms, but they were still highly contagious, so they could spread the virus without knowing it. Others infected with the virus experienced fevers, sore throats, and body aches.

For some, the effects of polio were more severe. Their muscles became paralyzed. Many people stricken with polio had to be put inside an iron lung, a metal tank-like machine that helped them breathe. Others had to use crutches or wheelchairs for the rest of their lives. 

Sick children were quarantined to prevent them from passing along the virus through coughs and sneezes. But polio still could spread easily, even through human waste in the water supply. 

Dr. Jonas Salk had been studying viruses for years when the polio outbreak swept the nation. In 1947, he began to work on a polio vaccine—a shot to prevent healthy people from catching the virus. 

“A vaccine takes a harmless part of the virus and shows it to your immune system,” explains Nicole Doria-Rose. She is a scientist at the National Institutes of Health. “Your immune system remembers the virus and is prepared to fight it off right away if you’re exposed to it.”

By 1953, Salk had created what he thought was a successful polio vaccine. Before sharing the news with the public, Salk wanted to test that the vaccine was safe. So he injected himself, his wife, and their three sons. A year later, nearly 2 million kids in three countries took part in a test of the vaccine. 

Finally, on April 12, 1955, doctors made an announcement that would change the world. Salk’s polio vaccine had been proved safe, effective, and ready for use.

Over the next decade, the number of polio cases dropped sharply. No one has caught the virus in the U.S. since 1979. Polio has since been eradicated throughout all of North America, South America, and Europe. 

Salk’s discovery saved countless lives and paved the way for many vaccines that followed—including the shots being used in the fight against Covid-19. Doria-Rose says the vaccines developed by Salk and other scientists have changed the world. 

“They have had the greatest impact of any medical invention ever in terms of the number of lives saved,” she says.

1. Why were kids with polio quarantined in the late 1940s and early 1950s?

2. How is a vaccine supposed to work, based on the article?

3. Why was April 12, 1955, an important day in America?