Immunity and vaccines

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  • Immunity and Vaccines
    • Protection
      • 1) Vaccines contain antigens that initiate production of memory cells without pathogen causing the disease. Become immune without symptoms
      • 2) Vaccines reduce occurrence of disease- those not vaccinated less likely to catch disease. Herd immunity
      • 3) Contain dead/weakened antigens
      • 4) May be injected/taken orally. Oral vaccines can be broken down by enzymes/may be too big to be absorbed into blood.
      • 5) Booster vaccines given to make sure memory cells produced
    • Antigenic variation
      • 1) Antigens on surface of pathogen activate primary response
      • 2) Second infection of same pathogen activate secondary response- don't get ill
      • 3: Some pathogens change surface antigens
      • 4) Memory cells produced from first infection will not recognise different antigens on second infection. Primary response carried out again
      • 5) Person gets ill again, primary response slow
      • 6) Difficult to develop vaccines against some pathogens e.g. HIV/ influenza
    • Flu
      • 1) Flu vaccine changes every year as antigens on flu virus change regularly and form new strains on virus.
      • 2) Memory cells produced from one strain will not recognise other strains with different antigens- immunologically distinct
      • 3) Every year different strains of influenza circulate population, different vaccine has to be made
      • 4) New vaccines are developed every year, most effective against recent strain chosen
      • 5) Government implements programme of vaccination using most suitable vaccine
    • Active Immunity
      • Immune system makes own antibodies
      • Natural: become immune after catching disease
      • Artificial: become immune after vaccination
      • Requires exposure to antigen, takes a while for protection to develop, memory cells produced, long term protection due to memory cells
    • Passive
      • Given antibodies made by different organism
      • Natural: mother provides antibodies to baby through placenta/milk
      • Artificial: Become immune after injection of antibodies from someone else
      • Doesn't require exposure to antigen, immediate protection, no memory cells produced, short term protection


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