Transcript Vaccines
VACCINES https://www.youtube.com/watch?v=rb7TVW77ZCs HISTORY OF VACCINES • Variolation to Vaccination • Variolation • Innoculation of smallpox into skin • Vaccination • Edward Jenner developed the modern practice of vaccination when he inoculated people with cowpox virus to protect them against smallpox. HOW DO VACCINES WORK? • “Trick” human immune system into producing antibodies or immune cells • Induce protection against real disease-causing microbes • Do not cause illness but cause production of T cells and Antibodies WHAT DO WE WANT TO ACHIEVE WITH VACCINES? • Herd Immunity • Large proportion of group is resistant whole group is resistant • Results from effective vaccination programs (90% vaccinated no spread of disease) IMMUNOLOGIC MEMORY KILLED INACTIVATED VACCINES • Also fight viruses • No danger of infection • Made by inactivating or killing the virus during the process of making the vaccine • Killed by treatment with heat or chemicals • Does not stimulate cell mediated immunity • Usually need booster vaccines • Examples • Salk Polio Vaccine and Rabies Vaccine TOXOID VACCINES • Prevent diseases caused by bacteria that produce toxins (poisons) in the body • • Some bacteria cause disease by producing toxins that invade the bloodstream Toxins are weakened so they can’t cause illness • Toxoids • The immune system will learn how to fight off the natural toxin after receiving the vaccine with a toxoid • Examples • • Diphtheria Tetanus and Pertussis (DTaP vaccine- contains diphtheria and tetanus toxoids) SUBUNIT VACCINES • Only use part of a bacteria or virus • Produce effective immune response without causing separate & potentially harmful immune reactions to the many antigens carried on microbe • Examples • DTaP vaccine (The pertussis component is an example of a subunit vaccine) • Typhoid • Hepatitis B NON-INFECTIOUS VACCINES The first three vaccines named in these notes are considered to be non-infectious -Will make B-memory cells and T-helper memory cells = good antibody response -Will not make memory killer T cells -Booster vaccines usually needed LIVE ATTENUATED VACCINES • Fight viruses • Closest to natural infection • Contain a version of the living virus that has been weakened so that it does not cause serious disease in people with healthy immune systems • Not everyone can receive them • • Children with weakened immune systems (ex: patients undergoing chemotherapy) Examples • • • Sabin Polio Vaccine (not currently recommended) Measles, Mumps, and Rubella Vaccine (MMR) Varicella (chickenpox) Vaccine LIVE ATTENUATED VACCINES -Makes memory cells: B-cells, T helper and Killer T cells - Usually life-long immunity Some viral shedding: can produce disease in immunocompromised host CONJUGATE VACCINES • Fight different type of bacteria • Bacteria have antigens (Ag) with an outer coating of sugar-like substances called polysaccharides • • These vaccines link together proteins or inactivated toxins from a 2nd organism to bacteria’s outer coat • • • Coating disguises the Ag • Coat isn’t recognized by immature immune systems of young infants therefore there is no response to it Enables baby's immune system to respond to combined vaccine & produce antibodies Causes immune response against disease-causing bacteria Examples • Haemophilus influenzae type B (Hib vaccine) SAFETY OF VACCINES • Benefits of vaccines far outweigh their risks • The American Academy of Pediatrics, the Centers for Disease Control and Prevention, and the Institute of Medicine all conclude that the benefits of vaccines outweigh their risks • Thimerosal is a preservative that was found in most vaccines in the past. But now: • • • Only one third of flu shots still have thimerosal NO other vaccines commonly used for children or adults contain thimerosal Research done over many years has NOT shown any link between thimerosal and autism, or other medical problems Source: http://www.nlm.nih.gov/medlineplus/ency/article/002024.htm Source: CHAPTER 22 VACCINATION