Communicable diseases Flashcards
Vaccination
the deliberate exposure of an individual to antigens from a. foreign source in order to provoke an immune response and provide immunity
immunisation
the process by which an individual develops immunity
Some diseases are not yet eradicated by vaccines
Very infectious, difficult to diagnose, difficult to achieve herd immunity etc
How vaccines provide immunity
- Injection of an antigen or weakened pathogen
- Activates the immune system resulting in an immune response
- Antigen engulfed by phagocytes and they become APC
- T helper cells are selected and activated- clonal selecton
- Divide by mitosis- clonal expansion
- They produce and release cytokines
- Cytokines activate B lymphocytes
- These also divide by mitosis, B plasma cells produced which secrete antibodies
- B memory cells produced
- Remain in the plasma
- Secondary response is quicker to the same pathogen
Subsequent infection
- Low antibodies produced after first exposure, as no memory cells
- After second exposure, the memory cells stimulated to divide rapidly
- So clonal expansion and clonal selection happen faster
- Memory cells differentiate in plasma cells
- Higher number of plasma cells produce antibodies faster and in greater numbers
Live attenuated vaccine
-Modified strains or bacteria or virus that are non-pathogenic
+provides strongest immune response
-Organism may revert to become pathogenic
Kiled inactivated vaccine
-Bacteria or viruses killed by heat or chemical treatment. Antigens remain intact
+more stable and safer than LAV
-Generates weaker immune response, booster needed
Toxoids
- toxins extracted and treated with formaldehyde
- stimulates production of antitoxins
+Safe to use
-may not provoke strong immune response
Subunit and Conjugate
Only specific antigens that promote immune response are extracted and used
-Can make vaccines that treats several strains
Artificial or recombinant
-Genes for antigens are transferred to harmless microorganisms
+immunnity to pathogens that can’t be easily inactivated
Vaccination program eg HPV
- Herd immunity
- Reduces the chance an infected person can pass on the disease to uninfected person
- Herd immunity protects those who cannot be immunised
Why vaccination programs change
- Change of antigens quickly
- New strains of pathogen formed
- memory cells will not recognise new srains
- so new strains will need a different vaccine
Biological problems developing vaccine
Mutation:
- Antigenic shift
- High mutation rate of pathogens so surface antigens change significantly
- Circulating antibodies will not be effective, as memory cells will not recognise different strains
- Each strain will need a different vaccine
Production and storage:
- Must be in sterile conditions
- Incubation may be costly
- Transportation cost
Biological problems implementing vaccine
- Live attenuated vaccines may revert and become virulent
- Malnutrition impacts on ability got immune system to respond strongly
Ethical problems developing vaccine
- Legal requirement to test on both animals and unaffected humans
- Very expensive
- Profit margins are small- pharmaceutical companies would rather produce medication
