Study Guide-Video-The Vaccine That Changed The World

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This 44:30 minute BBC documentary details the development of the polio vaccine. Much of the story behind the development of this vaccine and the pressing need for it during the 1930s, 1940s, and 1950s may be unfamiliar to your students. They may have heard of polio as a disease that infected people years ago, but they probably don’t know how devastating its effects were to thousands of children.

The video describes the “polio season”—the time of year when polio cases increased, peaked, and then, for some reason, went away. But, the season came back every year for decades. Parents were fearful of their children contracting this disease which could leave their child paralyzed, crippled, or in an iron lung—if they survived.

The video details the how the vaccine was developed, the incredible work done by the Jonas Salk research team in a basement lab in Pittsburgh, Pennsylvania, and the courageous Americans who banded together to donate money for the research effort and who volunteered their children to test the vaccine in hopes that they would be protected from the disease.

Scientific research is highlighted as is the real world of competing scientists. Footage from the 1950s adds a valuable context to the documentary detailing “the vaccine that changed the world.”

Note: Polio still exists in the world. Cases have decreased 99% since 1988 from 350,000 cases to 37 in 2016 (WHO). Global efforts have resulted in the dramatic reduction. Only 3 countries now report polio virus transmission:  Pakistan, Afghanistan, and Nigeria.

As long as the polio virus is present in the world, it can be imported into a country and spread to unvaccinated populations. Polio remains a threat to unvaccinated people.

Study Guide

  1. In the 1930s, 40s, and 50s, why did parents dread summer?

This was the “polio season”. Cases began to appear in late May each year and increased throughout June and July; cases peaked in August. The disease mainly affected children under 5 years old. No one knew why it happened or why it would strike in one city and not in a nearby city. They only knew that every year, more children would come down with this insidious disease which may paralyze or kill them.

  1. Data showed how much polio increased throughout the decades. Describe the increase.

In the 1930s, in the worst year for polio infections in that decade, 9,700 people were infected. Cases increased in the 1940s and in one year in the 1950s, 57,000 people were infected.

  1. What was another name for polio? Why?

Infantile paralysis. It was called that because it most often infected small children and it often ended in varying degrees of paralysis.

  1. By the 1950s, it was known that polio was a viral disease, but there was no way to prevent it and they did not know how it was spread. What were some of the ideas about polio’s transmission methods?

Ideas included that polio was spread by cats, by fleas, by organ grinders’ monkeys, by bananas from South America and by public pools. There was no scientific evidence for these ideas but people were desperately trying to avoid anything that might make their children sick.

  1. How is polio actually spread?

The polio virus is spread through sneezing, coughing, and contact with human wastes infected with the virus.

  1. How does the polio virus attack the body?

The virus reproduces in the mouth and in intestines, gets into the blood and invades the nervous system. It kills the anterior horn cell in the central nervous system. This cell controls muscle movement. Paralysis results from anterior horn cell function disruption.

Note: Other anterior horn cell diseases include spinal muscular atrophy and amyotrophic lateral sclerosis. These diseases, including polio, produce generalized weakness, poor or absent reflexes, and sometimes, paralysis.

  1. What are the effects of a polio infection?

Sometimes, the infection came and went with no lasting effects.  Sometimes the disease paralyzed people. This aspect that was particularly bad if the paralysis affected breathing mechanisms. If the diaphragm was affected, a child could not breathe and had to be put in an iron lung.

  1. What was an iron lung? What did it do?

An iron lung was an early respirator. It inflated and deflated the lungs of people whose diaphragms did not work because of polio infection.

  1. President Franklin D. Roosevelt was afflicted with polio. What did he do to try to combat polio outbreaks?

He founded what later became the March of Dimes organization in 1938 whose goal was developing a polio vaccine and helping those who had been infected. The organization raised millions for research and patient help.

  1. How do vaccines produce immunity?

Vaccines contain dead or weakened viral particles. The viral particles stimulate the body’s immune system to produce antibodies against the disease. The antibodies in the blood fight off the disease virus when exposed and the vaccinated person does not contract the disease. Protection against disease is called immunity.

  1. What was different about Salk’s vaccine as compared to other vaccines at that time?

At that time, leading scientists thought that vaccines had to contain live virus in order to be effective. Jonas Salk thought that immunity to polio could be produced by a vaccine containing dead virus.

  1. Who was Dr. Albert Sabin and what was his approach to polio research?

He was a virologist from Cincinnati who was also working on a polio vaccine. He thought the vaccine had to be made from live virus in order to be effective. He was a leading scientist at that time and many other scientists listened to his opinion rather than Dr. Salk’s opinion on the issue. They did not support Dr. Salk’s research.

  1. Vaccines work to provide protection against disease in two ways. What are they?

They produce individual protection against a disease (immunity) and they can produce herd immunity. Herd immunity results when enough of a population has been immunized so that an outbreak is stopped before it becomes an epidemic. If there aren’t enough susceptible people in a population, the virus cannot spread. This type of immunity protects people who cannot be immunized because they are too young or because they have health factors which do not allow them to get vaccinated.

  1. The first small-scale tests of Salk’s vaccine were successful.
    a) Why did they have to test a much larger group?

The first test group was not large enough for a definite conclusion that the vaccine was effective. They needed a larger test population. Also, the first group’s test subjects had all been previously infected with polio. Although the vaccine was effective in providing immunity for subsequent infections, they did not know if the vaccine would work on subjects who had no previous infection with the polio virus.

b) Why did they have the test administered by a group outside the University of Pittsburgh (where Salk was located)?

They wanted an environment that would guarantee objectivity.  Although Salk’s researchers would follow science methodology and remain objective, the scientific community and people funding the clinical trial wanted to ensure that objectivity.

c) Why was the clinical trial placebo-controlled?

A placebo is a harmless substance that is used as a control in comparison to a substance being tested. In the polio vaccine clinical trial, a harmless substance was injected into some people in the trial and other people got the polio vaccine. Then, results of each group could be compared to see if the vaccine was truly effective.

  1. Why did Jonas Salk think the placebo-controlled clinical trial presented a “moral dilemma”?

One-half of the children in the test received a placebo and one-half of the children received the polio vaccine. He thought that it was morally reprehensible to withhold the vaccine from some children and not give them protection from polio.

  1. What were the results of the large-scale, placebo-controlled clinical trial of the Salk vaccine?

The vaccine was successful in producing immunity in 80-90% of people tested.

  1. Pharmaceutical companies make billions of dollars on the production and sale of vaccines. How much money did Dr. Salk make on his polio vaccine?

Other than his salary, Dr. Salk did not make money from his development of the vaccine. He contributed the vaccine development freely to the world.