21 - Immunisation

Question 1

Contra indications (reasons to not be immunised)

Answer 1

• Anaphylaxis to previous dose
• Immunosuppression – do not give live vaccine (MMR, BCG)
• Postpone if acutely unwell

Question 2

What is herd immunity?

Answer 2

• Percentage of people that must be vaccinated for the population to be effectively protected from infection with the pathogen

Question 3

What percentage of the population needs to be immunised to satisfy herd immunity?

Answer 3

80-85%

Question 4

What are the features of an effective vaccine?

Answer 4

• Safe – must not cause illness itself
• Protection – must protect against the vaccine
• Longevity – should give long lasting protection
• Neutralising antibodies – introduced to protect against pathogens such as polio and many toxins and venoms
• Protective T cells – must e induced to protect against pathogens such as TB
• Practicality – must be cheap to produce and easy to administer

Question 5

What is a vaccination?

Answer 5

active immunisation – changes immune system fundamentally to induce immunity
o Vaccines can be inactivated forms of the virus or live, weakened versions (attenuated)

Question 6

What is the difference between inactivated and attenuated virus?

Answer 6

o Inactivated – virus is unable so replicate and generates humoral immunity
 DPT
o Attenuated – virus can replicate but doesn’t cause disease. Leads to the generation of humoral and cell-mediated immunity
 MMR, BCG

Question 7

What is passive immunisation?

Answer 7

will protect you but has not changed your immune system, e.g. give protective antibodies or maternal transfer of antibodies through the placenta and breast milk
o Often given to counteract insect and animal venom such as snake bites
o Usually horse serum is used – can develop immune response against the serum (serum syndrome)
o Not long-lasting – antibodies only last around 3 months