Who Developed the Polio Vaccine?

National Library of Medicine

Shortly before the turn of the 20th century, the first case of paralytic polio in the United States was reported in Vermont. And what had began as a health scare would, over the next several decades, turn into a full blown epidemic as the virus known as infantile paralysis spread among children across the country. In 1952, the height of the hysteria, there were as many as 58,000 new cases. 

It was undoubtedly a scary time back then.

The summer months, normally a relaxing time for many youth, was considered polio season. Children were warned to stay away from swimming pools because they can easily catch the disease by going into infected waters. And in 1938, President Franklin D. Roosevelt, who was infected at age 39, helped create the National Foundation for Infantile Paralysis in an effort to combat the disease. 

In the late 1940's, the foundation began sponsoring the work of a researcher at the University of Pittsburgh named Jonas Salk, who’s biggest achievement to date was the development of a flu vaccine that used killed viruses. Normally, weakened versions were injected to cause the immune system to produce antibodies capable of recognizing and killing the virus. 

Salk was able categorize the 125 strains of the polio viruses under three basic types and wanted to see if the same approach would also work against the Polio virus.

Up to this point, researchers weren’t making progress with live viruses. Dead viruses also offered the key advantage of being less dangerous since it wouldn’t lead to inoculated people accidentally getting the disease. 

The challenge, though, was to be able to manufacture enough of these dead viruses to mass produce the vaccines.

Fortunately, a method for making dead viruses in large quantities was discovered just a few years earlier when a team of Harvard researchers figured out how to grow them inside animal-cell tissue cultures rather than having to inject a live host. The trick was using  penicillin to prevent bacteria from contaminating the tissue. Salk’s technique involved infecting monkey kidney cell cultures and then killing the virus with formaldehyde. 

After successfully testing the vaccine in monkeys, he began trialling the vaccine in humans, which included himself, his wife and children. And in 1954, the vaccine was field tested in almost 2 million children under the age of ten in what was the largest public health experiment in history. The results, reported a year later, showed that the vaccine was safe, potent and 90 percent effective in preventing children from contracting polio. 

There was one hiccup, however. Administration of the vaccine was momentarily shut down after 200 people were found to have gotten polio from the vaccine. The researchers were eventually able to trace the adverse effects to a defective batch made by one drug company and vaccination efforts resumed once revised production standards were established.

 

By 1957, the cases of new polio infections had dwindled done to under 6,000. Yet despite the dramatic results some experts still felt that Salk’s vaccine was insufficient in fully inoculating people against the disease. One researcher in particular named Albert Sabin argued that only an attenuated live-virus vaccine would confer lifetime immunity. He had been working on developing such a vaccine around the same time and was figuring out a way for it to be taken orally. 

While the United States backed Salk’s research, Sabin was able to get support from the Soviet Union to conduct trials of an experimental vaccine that used a live strain on the Russian population. Like his rival, Sabin also tested the vaccine on himself and his family. Despite a slight risk vaccinations resulting in Polio, it was proven to be effective and cheaper to manufacture than Salk’s version.

The Sabin vaccine was approved for use in the U.S. in 1961 and would later replaced the Salk vaccine as the standard for preventing Polio. 

But even to this day, the two rivals never did settle the debate over who had the better vaccine. Salk always maintained that his was the safest and Sabin would not concede that injecting a killed virus can be  as effective than conventional vaccines. In either case, both played a crucial role in nearly eradicating what was once a devastating condition.