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Antibiotics and Vaccines

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  • 1:10 Sanitation
  • 2:25 Vaccines
  • 4:31 Types of Vaccines
  • 7:50 Antibiotics
  • 10:32 Lesson Summary
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Lesson Transcript
Instructor: Heather Higinbotham
Do you know why children must get regularly vaccinated? Have you ever wondered how an antibiotic works and why they are so widely prescribed? If so, this lesson will help you to understand how changes in medicine have almost eliminated several deadly diseases and added decades to the average person's lifespan.

Rise in Life Expectancy

The use of antibiotics and vaccines have led to a rise in life expectancy over time
The rise of life expectancy

In 1900, the average life expectancy in the United States was 48-51 years, and the top three leading causes of death were pneumonia, tuberculosis and diarrhea, all of which were caused by infectious diseases. However, by 1997, the average life expectancy rose to 74-80 years, and pneumonia and influenza combined were the sixth leading cause of death and the only infectious diseases to crack the top ten. Many once fearsome and devastating diseases, like smallpox, polio, syphilis, tuberculosis, measles, cholera and the bubonic plague, have either been nearly eradicated or are now easily treated with modern medicine. The dramatic increase in the average life expectancy, not only in the U.S. but around the world, in the last 160 years has been accomplished in large part due to the effective prevention and treatment of infectious diseases through the use of sanitation, antibiotics and vaccines.

Sanitation

Experiments performed by Louis Pasteur in the 1860s convinced the Western scientific community that the germ theory of disease was correct. The germ theory of disease is a scientific theory which states that infectious diseases are caused by microscopic organisms that must be transferred from one host to another in order to spread. The acceptance of germ theory led to wide-scale changes in medicine, food preparation and waste disposal. Prior to the 1860s, medical practices were extremely unsanitary. Washing hands and instruments before and after surgeries was not a common practice, and the more dried blood and gore that a surgeon had on his surgical clothes, the more prestige and experience he was assumed to have. However, after the realization that disease was caused by microorganisms that could be transferred by body fluids, food and waste, wide-scale changes in medicine, food preparation and waste disposal were implemented in the Western World. Death rates from infection in hospitals fell, and between 1850 and 1900, the average life expectancy in the U.S. jumped up by more than 25% from 39 years to almost 50 years.

Vaccines

Edward Jenner performed the first successful vaccination in 1796
Inventor of the first vaccine

Another breakthrough in medicine that has contributed to the rise in life expectancy over the last 160 years is the widespread use of vaccines. Vaccines are non-disease causing variants, or derivatives of pathogens, that are used to create immunological memory against the pathogens themselves. Strangely enough, the first successful vaccination to be tested against a challenge with a pathogen was performed in 1796 by Edward Jenner, more than 60 years before the germ theory of disease was widely accepted by the scientific community.

It had been observed that milk maids did not often contract smallpox, which was in sharp contrast to an estimated 60% of the general population that contracted the disease. However, almost all milk maids did contract a related, but nonlethal disease, called cowpox, from the udders of the cows that they milked. It was postulated that contracting cowpox made a person resistant to smallpox infection, so Jenner took it upon himself to test this hypothesis. He took pus from the cowpox blisters of a milkmaid and inoculated a young boy with it. The inoculation produced a mild fever and some short-lived discomfort in the boy but no other signs of infection. Two and a half weeks later, Jenner injected the boy with smallpox material, and the boy remained healthy. Jenner repeated the smallpox challenge 20 times, and the boy never showed any signs of smallpox infection.

Jenner then successfully repeated his experiment on 23 additional people. Jenner's findings were published and quickly spread among physicians in Europe and America. By 1801, physicians all across Europe and even a few in North America started to use Jenner's vaccination procedure. Increased use of the vaccine and a concerted effort by the World Health Organization more than a century later to rid the world of smallpox through vaccination, resulted in complete eradication of smallpox by 1977.

Types of Vaccines

The smallpox vaccine is an example of a live vaccine, which uses live, infectious virus as the actual vaccine. Live vaccines are usually just weaker, less dangerous forms of the disease-causing virus. These so called live, attenuated vaccines are created in the laboratory under conditions that promote less harmful characteristics of a virus. In the case of the smallpox vaccine, nature provided a much less dangerous alternative, which could still impart immunity to smallpox. A rather fortunate coincidence for humankind and modern medicine, especially given how deadly and infectious smallpox was.

Some vaccines called inactivated vaccines are created by killing or inactivating the pathogen and then using it as the vaccine itself. An example is the pertussis vaccine that protects against whooping cough. Inactivated vaccines are easier to create than live, attenuated vaccines and don't carry the risk of mutating back into a disease-causing form. However, because this type of vaccine isn't active and therefore, doesn't infect the body's cells, the immune response that it produces is not as strong as an immune response to a virus that is actively infecting cells. The resulting immunity is also not as strong and fades more quickly over time because fewer memory cells are produced. Therefore, inactivated vaccines must be administered more than once, sometimes three or more times to create a strong enough immunity to the infectious agent. Each injection of the vaccine after the initial injection is called a booster shot, and with each additional shot, more memory cells are produced and the body's immunity is strengthened.

In certain types of bacterial infections, the disease is caused by a toxin produced by the organism. In most of these situations, it has been found that the toxin can be inactivated with formalin and used as a toxoid vaccine. An example is the tetanus vaccine. An immune system primed against a toxin will be able to identify and destroy the toxin before it can do too much harm, especially if booster shots are given.

Bacteriologist Alexander Fleming discovered the antibacterial properties of penicillin in 1928
Discovery of penicillin

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