Salk Develops a Polio Vaccine Summary

  • Last updated on November 10, 2022

Locale Pittsburgh, Pennsylvania

Summary of Event

Poliomyelitis (polio) is an infectious disease that can adversely affect the central nervous system, causing paralysis and great muscle wasting in serious cases. It is caused by the destruction of motor neurons (nerve cells) in the spinal cord. Epidemiologists believe that polio has existed since ancient times, and evidence of its presence in Egypt, circa 1400 b.c.e., has been presented. Fortunately, the Salk vaccine and the later Sabin vaccine prevent the disease. Consequently, except in underdeveloped nations, polio is rare nowadays. Once a person develops polio, however, there is still no cure for it. Fortunately, a large number of polio cases end without paralysis or any observable effect. [kw]Salk Develops a Polio Vaccine (July 2, 1952) [kw]Polio Vaccine, Salk Develops a (July 2, 1952) [kw]Vaccine, Salk Develops a Polio (July 2, 1952) Vaccines;poliomyelitis Poliomyelitis Vaccines;poliomyelitis Poliomyelitis [g]North America;July 2, 1952: Salk Develops a Polio Vaccine[03810] [g]United States;July 2, 1952: Salk Develops a Polio Vaccine[03810] [c]Health and medicine;July 2, 1952: Salk Develops a Polio Vaccine[03810] [c]Science and technology;July 2, 1952: Salk Develops a Polio Vaccine[03810] Salk, Jonas Francis, Thomas, Jr.

Polio is often called infantile paralysis. This results from the fact that it is most often seen in children. It is caused by a virus and begins with body aches, a stiff neck, and other symptoms that are very similar to those of a severe case of influenza. In some cases, within two weeks after its onset, the course of polio begins to lead to muscle wasting and paralysis. Even though other communicable diseases strike more people each year than polio, very few of them are viewed with more fear, because almost none produce such drastic, long-lasting consequences.

On April 12, 1955, the world was thrilled with the announcement that Jonas Salk’s poliomyelitis vaccine could prevent the disease. It was reported that schools were closed in celebration of this event, many universities awarded Salk honorary degrees, he was given a Congressional Gold Medal, and France made him a member of the Legion of Honor. Salk, the son of a New York City garment worker, had become one of the most well known and publicly venerated medical scientists in the world.

Vaccination is a method of disease prevention whereby a small amount of a virus is injected into the body to prevent a viral disease by immunization. The process depends on the production of antibodies (body proteins that prevent the disease) in response to the vaccination. Vaccines are made of weakened or killed virus preparations. The technique of vaccination was pioneered, in 1796, by Edward Jenner Jenner, Edward , an English physician who prepared a vaccine for smallpox. Jenner used the weak cowpox virus in his vaccine and made smallpox, which had killed 60 million people in the eighteenth century, rare in civilized countries.

Salk’s work, leading to the development of the polio vaccine, began in 1938. At that time he was a senior medical student at New York University Medical School. There, he came into contact with the famous microbiologist Thomas Francis, Jr., who was studying methods for developing a “flu vaccine” Vaccines;influenza Influenza by killing influenza viruses without loss of their ability to stimulate antibody production. Salk worked with him for several months, learning many of the important techniques of immunology and virology. Salk received a National Research Council fellowship to work with Francis, and their collaboration led to production of an effective flu vaccine used during World War II.

In 1947, Salk became the head of the Virus Research Laboratory at the University of Pittsburgh School of Medicine University of Pittsburgh School of Medicine Virus Research Laboratory . He continued his efforts to produce much better influenza vaccine and began to study polio. Salk’s first work on polio involved participation in identification of the number of distinct types of polio virus that existed among the 125 strains that had been observed by the scientific community.

This endeavor was part of a multicenter study carried out at the University of Pittsburgh (by Salk), the University of Kansas (by Herbert A. Wenner), the University of Utah (by Louis P. Gebhardt), and the University of Southern California (by John F. Kessel). This information was required before a polio vaccine could be attempted, because it would tell researchers how many different types of virus the public needed to be protected against. After a long, arduous effort, Salk and his associates found that all of the known strains of polio virus belonged to three distinct groups (Types I, II, and III). Therefore, production of an effective polio vaccine required immunization against three viral types.

Actualization of the Salk vaccine was aided tremendously by the earlier work of the Harvard University microbiologists, John Franklin Enders Enders, John Franklin , Frederick Chapman Robbins Robbins, Frederick Chapman , and Thomas H. Weller Weller, Thomas H. . These scientists developed the first practical means to grow large quantities of polio virus outside the body, by the use of monkey kidney tissue cultures. Before their discovery, it had been possible to prepare only small quantities of the virus. The Salk vaccine was produced in two steps: First, polio viruses were grown in monkey kidney tissue cultures, similar to those developed by Enders and his colleagues. Then, these polio viruses were killed by treatment with just the right amount of formaldehyde to produce an effective vaccine. The killed-virus polio vaccine was found to be safe and to cause the production of antibodies against the disease, a sign that proved it should prevent polio.

In early 1952, Salk tested a prototype vaccine against Type I polio virus on children who were afflicted with the disease and were thus deemed safe from reinfection. This test showed that the vaccination greatly elevated the concentration of polio antibodies in these children. On July 2, 1952, encouraged by these results, Salk vaccinated forty-three children who had never had polio with vaccines against each of the three virus types. Vaccines against Type I, Type II, and Type III virus were given to thirty, two, and eleven children, respectively. All inoculated children produced high levels of polio antibodies and none of them developed the disease. Consequently, the vaccine appeared to be both safe in humans and likely to become an effective public health tool.

In 1953, Salk reported these findings in the Journal of the American Medical Association. In April, 1954, nationwide testing of the Salk vaccine began, via the mass vaccination of American schoolchildren. This effort was directed and evaluated by Salk’s former mentor, Thomas Francis. It involved three test groups of six- to nine-year-old children. The first group was composed of nearly 423,000 children, who each received three spaced-out vaccine inoculations. The 1.3 million doses of Salk vaccine used were produced by five pharmaceutical companies.

Another, similar-sized group of children was given placebo injections (placebo is a treatment that contains no medication, given for comparison with a drug treatment being tested). Finally, a third, large group of children was observed but not injected. The results of the trial were electrifying. The vaccine was safe, and it greatly reduced the incidence of the disease. In fact, it was estimated that Salk’s vaccine gave the schoolchildren 60-90 percent protection against polio.

Salk was instantly praised. Then, several cases of polio occurred as a consequence of the vaccine. Its use was immediately suspended by the surgeon general, pending a complete examination. Soon, it was evident that all the cases of vaccine-derived polio were attributable to faulty batches of vaccine made by one pharmaceutical company. Salk and his associates were in no way responsible for the problem. Appropriate steps were taken to ensure that such an error would not be repeated, and the Salk vaccine was again released for use by the public.


The first reports on the polio epidemic occurred on June 27, 1916, when one hundred residents of Brooklyn, New York, were afflicted. Soon, the disease had spread. By August, twenty-seven thousand people had developed polio. Nearly seven thousand afflicted people died, and many survivors of the epidemic were permanently paralyzed to varying extents. In New York City alone, nine thousand people developed polio and two thousand died. Chaos reigned as large numbers of terrified people attempted to leave and were turned back by the police. Smaller polio epidemics occurred throughout the nation in the years that followed (for example, the Catawba County, North Carolina, epidemic of 1944).

A particularly horrible aspect of polio was the fact that more than 70 percent of polio victims were small children. The summer months became a dreaded time for children likely to catch polio. Adults caught it too; the most famous of these adult polio victims was Franklin D. Roosevelt. There was no cure for the disease. The best available treatment was physical therapy.

As of August, 1955, more than 4 million polio vaccines had been given. The Salk vaccine appeared to work very well. This can be shown by comparison of the number of cases reported in 1955 and 1956—28,985 and 14,647, respectively. It appeared that polio was being conquered. By 1957, the number of cases reported nationwide had fallen to 5,894. Thus, in two years, its incidence had dropped by about 80 percent.

This was very exciting, and soon other countries clamored for the vaccine. By 1959, ninety other countries had been supplied with the Salk vaccine. Worldwide, the disease was being eradicated, and nowadays it is quite rare.

Salk received many honors, including honorary degrees from American and foreign universities, the Lasker Award, a Congressional Medal for Distinguished Civilian Service, and membership in the French Legion of Honor. He received neither the Nobel Prize nor membership in the American National Academy of Sciences. It is believed by many that this neglect was a result of the personal antagonism of some of the members of the scientific community, who strongly disagreed with his theories of viral inactivation. Vaccines;poliomyelitis Poliomyelitis

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Berg, Roland H. Polio and Its Problems. Philadelphia: J. B. Lippincott, 1948. The book gives a view of polio before the Salk vaccine, including frightening national polio epidemics, the campaign against polio by the National Foundation for Infantile Paralysis, and false starts toward chemical cures and polio vaccines. Also explores useful physical therapy for polio victims, including that used at the Warm Springs Foundation, and Sister Kenney’s work.
  • citation-type="booksimple"

    xlink:type="simple">Carter, Richard. Breakthrough: The Saga of Jonas Salk. New York: Trident Press, 1965. This biography carefully describes Salk’s life and the saga of development of the polio vaccine. It is realistic and includes both Salk’s triumphs and tribulations. It also outlines the stages of development of victory against polio.
  • citation-type="booksimple"

    xlink:type="simple">Cohn, Victor. Sister Kenney: The Woman Who Challenged the Doctors. Minneapolis: University of Minnesota Press, 1975. This biography describes the life work of nurse Sister Elizabeth Kenney, whose treatment of polio victims revolutionized polio physical therapy, the only avenue of treatment until the Salk vaccine. It emphasizes her ability and describes her battle to win support for a therapeutic procedure that was superior to that used by physicians of the time.
  • citation-type="booksimple"

    xlink:type="simple">Kovacs, Ernest. The Biochemistry of Poliomyelitis Viruses. New York: Pergamon Press, 1964. This book describes various aspects of the purification, biochemistry, and epidemiology of polio viruses. It also deals with the state of cells infected with polio viruses and the role of heredity in polio. The book is most useful to readers who desire detailed information on the viruses. It contains more than one thousand references.
  • citation-type="booksimple"

    xlink:type="simple">Melnick, Joseph L. “Poliomyelitis.” In McGraw-Hill Encyclopedia of Science and Technology. 9th ed. New York: McGraw-Hill, 2002. This brief summary of poliomyelitis presents a description of polio virus and its host range, the pathology of polio, the methodology for its diagnosis, and brief descriptions of the Salk and Sabin vaccines. References are given for additional information on tissue culture, animal viruses, and the polio vaccines.
  • citation-type="booksimple"

    xlink:type="simple">Rowland, John. The Polio Man: The Story of Dr. Jonas Salk. New York: Roy, 1960. This brief, chatty biography of Jonas Salk is best suited for young readers. Yet, it contains interesting information about Salk and the development of the Salk vaccine. One of its strongest points is the development of Salk’s career.

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Categories: History