[5.6] vaccinations

Question 1

what are the 4 types of immunity?

Answer 1

1. active natural immunity
2. active artificial immunity
3. passive natural immunity
4. passive artificial immunity

(active = long term, passive = short term)

Question 2

what is active immunity?

Answer 2

• primary immune response occurs due to exposure to specific antigen
• so memory B + T lymphocytes are produced
• so secondary immune response is possible if re-exposed to the same strain with the same specific antigen

Question 3

what is an example of active natural / active artificial immunity?

Answer 3

• natural = due to infection leading to exposure to specific antigen
• artificial = due to vaccination leading to exposure to a specific antigen

Question 4

what is passive immunity?

Answer 4

• no exposure to antigen
• so, no primary response so no memory cells made
• so, no secondary response is possible
• therefore, you have to get antibodies from elsewhere
• quicker than active immunity

Question 5

what is an example passive natural / passive artificial immunity?

Answer 5

• natural = antibodies directly supplied during pregnancy from mother to baby via placenta and through breast milk for early protection
• artificial = direct injection of antibodies into the bloodstream as an emergency precaution if possibly exposed to a dangerous pathogen eg. rabies virus

Question 6

what are some features of an effective vaccination programme?

Answer 6

• economically available in sufficient quantities to immunise most the vulnerable population
• few side effects
  > unpleasant side effects may discourage individuals in the population from being vaccinated
• means of producing, storing and transporting the vaccine must be available
  > this involves technologically advanced equipment, hygienic conditions, and refrigerated transport
• means of administering the vaccine properly at the appropriate time
  > this involves training staff with appropriate skills at different centres throughout the population
• must be possible to vaccinate the vast majority of the vulnerable population to produce herd immunity

Question 7

what is herd immunity?

Answer 7

• when a sufficiently large proportion of the population has been vaccinated so it is difficult for a pathogen to spread within that population
• the concept is based on the idea that pathogens are passed from individual to individual when in close contact
• where the vast majority of the population is immune, it is highly improbable that a susceptible individual will come in contact with an infected person
• in this way those individuals who are not immune to the disease are nevertheless protected

Question 8

why is herd immunity important?

Answer 8

• it is never possible to vaccinate everyone in a large population
  > babies and very young are not vaccinated as their immune system is not yet fully functional
• could also be dangerous to vaccinate those who are ill or have a compromised immune system

Question 9

why may vaccinations not eliminate a disease?

Answer 9

• vaccination fails to induce immunity in certain individuals eg. those with defective immune systems
• individuals may develop disease immediately after vaccination but before their immunity levels are high enough to prevent it. these individuals may harbour the pathogen and reinfect others
• pathogen may mutate frequently, so its antigens change suddenly. vaccine becomes ineffective, as immune system does not produce the antibodies to destroy the pathogen (concept of antigenic variability)
• too many varieties of a particular pathogen so it is impossible to develop a vaccine that is effective against them all
• some pathogens ‘hide’ from the body’s immune system by either concealing themselves inside cells or living in places out of reach eg. intestines
• individuals may have objections to vaccination for religious, ethical or medical reasons

Question 10

what are some ethical considerations of vaccines?

Answer 10

• development of vaccines will involve animal testing, and the inevitable death of some animals: to what extent is this acceptable and why?
• which animals would it be acceptable to use for testing and why?
• once a vaccine has reached the human trial stage, what factors should be considered to decide who the vaccines should be tested on?
• should people be paid for being part of a vaccine trial?
• what severity of side effects from a vaccine can be considered acceptable?
• once a vaccine programme has successfully reduced the spread of a disease, should money continue to be spent on the programme, or on other health concerns?
• is the use of experimental (ie. not fully trialled) vaccines acceptable, and if so, in what circumstances?