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The discovery of the polio vaccine was an important medical and scientific breakthrough because it saved many lives since the 1950s. In the summer of 1916 the great polio epidemic struck the United states. By the 1950s hundreds of thousands of people had been struck by the poliomyelitis. The highest number of cases occurred in 1953 with over 50,000 people infected with the virus.

When hygienic conditions were poor polio attacked infants. The disease was spread by contaminated water and contact with fecal contamination. Many infants died when the conditions were poor. But as conditions improved the virus spread differently. It was spread more through playmates and family members, the contamination came from the nose and throat. By the early 1950s, twenty-five percent of paralytic cases occurred in people 21 years old or older.

Jonas Salk M.D. developed the polio vaccine. Salk’s vaccine was composed of a “killed” polio virus. This virus kept the ability to immunize while preventing the infection of the patient. Later a “live” vaccine was developed from the live polio virus. This “live” vaccine could be administered orally as opposed to the “killed” vaccine which required an injection. There was some evidence that the “killed” vaccine didn’t completely eliminate the virus in the patient. United States public health authorities decided to distribute the oral “live” vaccine to eliminate the polio virus instead of Salk’s “killed” vaccine. Unfortunately, the “live” vaccine infected some people instead of immunizing. Countries that used Salk’s “killed” vaccine have nearly eradicated the virus.

Jonas Salk received his medical degree in June 1939 from New York University School of Medicine. Dr. Salk moved to Ann Arbor, Michigan in 1942 to begin research at the University of Michigan. In 1947 Jonas Salk went to Pittsburgh even though being advised against it, to work at the University of Pittsburgh School of Medicine. Dean William McEllroy talked Salk into joining the university full-time. Though the school’s research budget was a grant from the American Society for the Study of High Blood Pressure in the amount of $1,800, he saw the opportunity to do two things. One was to continue the work he was doing on influenza, second was to begin working with the polio virus. A few months after arriving in Pittsburgh, Salk was visited by the director of research at the National Foundation for Infantile Paralysis. The director asked Salk if he would be willing to participate in a polio typing program. “I had no experience working with polio, but it provided me with an opportunity. . .” Salk said in an interview. This gave Salk a chance to get funding, equipment, a laboratory facility, and to hire a staff to work for and with him.

Salk’s previous work gave him the idea that a killed virus could in fact work when others thought it couldn’t. To type the polio virus Salk infected monkeys with polio by injecting it into them or feeding it to them. If a monkey survived it built up antibodies to protect against the virus. The monkeys that survived were then given another type of virus to see if the same antibodies protected against the second type. If it did, it told Salk and his assistants that the two types were related. If it did not, that told Salk that they were not related. Eventually Salk and his assistants used 17,500 monkeys in the typing research.

Two other polio researchers, working independently, helped Salk look for a safe vaccine. Dr. Isabel Morgan from Johns Hopkins University was trying to find a vaccine that would keep the monkeys from being infected with the polio virus. Dr. Morgan killed the polio virus with formalin, thus creating polio antibodies in monkeys without infecting them. But Dr. Morgan’s ability to grow the polio virus antibodies in the nervous tissue of monkeys. It would not be beneficial for humans because in previous research it had been found that humans are highly allergic to other animal’s nervous tissue. Though it wasn’t the end, this was very good news. Many other researchers believed that only a live, weakened polio virus could be the only effective vaccine. Dr. Morgan proved them wrong.

Around the same time as infecting the monkeys and finding a cure for them, another great breakthrough came. Dr. John F. Enders of Boston reported successfully growing a polio virus in a test tube containing non-nervous human tissue.

On July 12, 1950, Dr. Jonas Salk formally asked the National Foundation for Infantile Paralysis (NFIP) for a grant to continue work on a polio vaccine. The grant was approved.

As soon as Salk had all his supplies and was beginning, a major problem developed. The workers were unable to duplicate the work of Dr. Enders; to go on, they had to find a way to grow polio virus in bottles with non-nervous human tissue. Dr. Salk found an error that the workers had made and soon various strains of polio virus were growing strong. Each strain was a different type and was killed to be placed in a safe vaccine.

The first strain was a Type I virus taken from a patient in Ohio with the name of Mahoney, this strain was named after Mahoney. The Type II strain was called MEF-1, it had been collected by doctors working with the American Middle East Forces that were stationed in Egypt during WWII. The body of a paralyzed little boy in Pittsburgh’s Municipal Hospital gave Dr. Salk the Type III, Salkett, strain.

Many experiments were needed now to create the vaccine. Salk and his assistants needed to find out how much formalin was needed to kill the virus just not enough to be a threat. They also needed to know how long and at what temperature the flasks of tissue and formalin needed to sit so as to be able to produce antibodies when injected in humans. In early 1952 Salk found a few answers. The viruses and the formalin were combined, so for every 250 parts of tissue-culture fluid there was 1 part of formalin. The mixture was allowed to develop for one to three weeks at at temperature of about 34?F. After a close study, most members of the NFIP agreed that the vaccine was both safe and effective.

On June 12, 1952 Salk went to the Watson Home for Crippled Children near Pittsburgh. He began a series of medical observations, he found that children with at least one type of polio had enough antibodies to ward off additional attacks by the same type of virus. Some children were injected with the vaccine and none showed any ill effects, but their levels of antibodies greatly increased. Soon enough children without polio were given the vaccine, none of them became ill but all were now protected from at least one type of polio.

By 1954 Salk had combined the different type vaccines into one vaccine. In 1954 the NFIP sponsored the final test of Salk’s vaccine. Almost two million school aged children were given the vaccine; by the following year it had proved to be safe and effective.

Indeed the polio vaccine was a breakthrough in medical science. Because of the work of Jonas Salk and others many people, including children and adults, are living healthy and productive lives because they are polio free. In developed countries it has been nearly eradicated.

Annotated Bibliography

The Hall of Science and Exploration: Interview page 1; 1-26-99 *http://www.achievement.org/autodoc/page/sal0bio-1*

The interview gave me knowledge of how Dr. Salk thought and felt about what he was doing. It also told me additional information about how he created his vaccine.

The Hall of Science and Exploration: Interview page 2; 1-26-99 *http://www.achievement.org/autodoc/page/sal0bio-2*

The interview gave me knowledge of how Dr. Salk thought and felt about what he was doing. It also told me additional information about how he created his vaccine.

The Hall of Science and Exploration: Interview page 3; 1-26-99 *http://www.achievement.org/autodoc/page/sal0bio-3*

The interview gave me knowledge of how Dr. Salk thought and felt about what he was doing. It also told me additional information about how he created his vaccine.

Hargrove, Jim. The Story of Jonas Salk and the Discovery of the Polio Vaccine. Childrens Press: Chicago, 1990

This book told me how Jonas Salk conducted his research and what some of his results were. This may have been my most helpful source.


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