Vaccination

1. Vaccination

2. 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

3. 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.

4. 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.

5. 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

6. 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 individual’s immune system to produce antibodies.

7. 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

8. 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.

9. Primary vs. Secondary Response

10. 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

11. 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

13. 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)