Vaccination

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Vaccination
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Vocabulary Check

• Vaccination conferring immunity to a disease by
  injecting an antigen (of attenuated
  microorganisms or inactivated component) so that
  the body acquires antibodies prior to potential
  infection
• Immunization the injection of a specific
  antigen, derived from a pathogen, to confer
  immunity against a disease
• Inoculation to introduce a microorganism into an
  environment suitable for its growth
• Attenuated weakened, with diminished or no
  ability to cause disease

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History of Vaccines

• Although it had long been recognized that those
  who had a disease once rarely contracted the same
  disease again, the process of immunization was
  not widely introduced until 1796 by Edward
  Jenner.
• Jenner realized that milkmaids who contracted
  cowpox, a mild disease, rarely got smallpox, a
  much deadlier disease.
• To test his hypothesis, Jenner inoculated an 8
  year old boy with fluid extracted from a cowpox
  pustule of an infected individual. The boy got a
  mild infection, but when he was later exposed to
  smallpox, he remained healthy.

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History of Vaccines

• Louis Pasteur later noticed a similar phenomenon
  with chicken cholera bacterium. Chickens which
  were inoculated with aged bacteria only got a
  mild version of the disease, and when inoculated
  again with fresh bacteria, they were immune. The
  bacteria had become attenuated.

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History of Vaccines

• Since this discovery, many vaccines have been
  produced. Some of the diseases which are
  vaccine-preventable are
• Hepatitis A B
• Influenza
• Measles
• Rabies
• Tuberculosis

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How Vaccines Work

• Vaccines are injected or administered by mouth.
  Very new vaccines are available as nasal sprays.
• Vaccines contain antigens to a disease which are
  inactivated or attenuated, and which stimulate an
  individuals immune system to produce antibodies.
  

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How Vaccines Work

• Vaccines can be manufactured in several ways
• from dead or attenuated bacteria
• from inactivated viruses
• from purified polysaccharides from bacterial cell
  walls
• from inactivated toxins
• from recombinant DNA produced by genetic
  engineering

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How Vaccines Work

• Antibodies produced in response attack the
  vaccine antigen, and memory cells persist in the
  body.
• It is these memory cells that will later prevent
  infection by the same antigen.
• This is termed active artificial immunity.

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Primary vs. Secondary Response
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Greatest Vaccine Success Story

• Eradication of Smallpox
• virus enters throat respiratory tract,
  targeting phagocytes and blood cells
• flu-like symptoms, leading to lesions, rash,
  scabs, severe scarring (if individual survives)
• mortality rate around 30
• transmitted by direct contact with infected
  individual

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Greatest Vaccine Success Story

• in 1950s there were approximately 50 million
  cases per year
• in 1967, World Health Organization (WHO) began
  the Intensified Smallpox Eradication Programme
• strategy mass vaccinations, followed by
  intensive surveillance
• 1979 declared smallpox eradicated

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Vaccine Side Effects

• Common side effects
• fever
• allergies
• minor swelling and pain at injection site
• Rare side effects
• panencephalitis (inflammation of the brain) from
  measles vaccine
• mutation of attenuated strain to virulent strain
• brain damage from unknown cause (Whooping cough
  vaccine)

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Benefits Dangers
Complete eradication of diseases (e.g. Smallpox) Excessive vaccination may reduce the effectiveness of the immune system to respond to new infections
Reduced death rate from diseases (e.g. measles) Vaccine immunity less effective than natural immunity (e.g. measles)
Reduced long term disabilities (e.g. blindness in rubella babies) Side effects such as possible autism from MMR vaccine