Immunisation

Question 1

Why immunise?

Answer 1

• Prevent individual disease
  (life-long, not just in children)
• Ideally, halt carriage & transmission
• > herd immunity is a side effect
• Ideally, eliminate > eradicate disease
• High coverage is operational target

Question 2

Given an example of passive immunity.

Answer 2

Immunoglobulin (Ig), which contains antibodies pooled together from the blood of many donors, can be injected into a person who needs antibodies. e.g. for Hep B

Question 3

What is the drawback of passive immunity?

Answer 3

This type of passive immunity, although effective, usually disappears within several weeks or months.

Question 4

What is active immunity?

Answer 4

Long-lasting immunity produced by the immune system in response to antigens.

Question 5

What is the persistence of protection for many years after natural infection or vaccination called?

Answer 5

Immunologic memory

Question 6

Which is the first antibody to be produced in an immune response?

Answer 6

IgM

Question 7

Which antibody is responsible for the secondary immune response?

Answer 7

IgG

Question 8

What happens when an antigen binds non-specifically to the variable region of an antibody?

Answer 8

Clonal expansion is triggered -> 1st wave of IgM production followed by IgG production.

Question 9

What is the function of IgG?

Answer 9

Binds tightly to antigen. Simultaneous complement binding facilitates the destruction of the invader.

Question 10

What are the advantages of live vaccines?

Answer 10

• Single dose often sufficient to induce long-lasting immunity
• Strong immune response evoked
• Local and systemic immunity produced

Question 11

What are the disadvantages of live vaccines?

Answer 11

• Potential to revert to virulence
• Contraindicated in immunosuppressed patients
• Interference by viruses or vaccines and passive antibody
• Poor stability
• Potential for contamination

Question 12

What are the advantages of inactivated/killed vaccines?

Answer 12

• Stable
• Constituents clearly defined
• Unable to cause the infection

Question 13

What are the disadvantages of inactivated/killed vaccines?

Answer 13

• Need several doses
• Local reactions common
• Adjuvant needed
  
  • keeps vaccine at injection site
  • activates antigen presenting cells
• Shorter lasting immunity

Question 14

What types of local reactions are possible with vaccines?

Answer 14

Pain, swelling or redness at injection site; small nodules may form at injection site

Question 15

What types of general reactions are possible with vaccines?

Answer 15

Fever, irritability, malaise, fatigue, headache, nausea, vomiting, diarrhoea, loss of appetite

Question 16

What happens to the frequency of reactions with live vaccines?

Answer 16

Freq of reactions decreases with no of doses - ab produced in response to live vaccine neutralises the small amount of vaccine virus in subsequent vaccine dose.

Question 17

What happens to the frequency of reactions with inactivated/killed vaccines?

Answer 17

Freq of reactions increases with no of doses - if ab levels are good from earlier vaccination, ab binds to the vaccine antigen in a subsequent dose leading to inflammatory response.

Question 18

How long after inoculation would you see a reaction with a killed/inactivated vaccine?

Answer 18

Generally within 48hrs following vaccination

Question 19

How long after inoculation would you see a reaction with a live vaccine?

Answer 19

occur according to time taken for virus to replicate e.g.
MMR vaccine:
reactions to measles component (malaise, fever, rash) tend to occur in 1st week following vaccination
reactions to rubella component (pain, stiffness or swelling of joints) tend to occur in 2nd week following vaccination
reactions to mumps component (parotid swelling) tend to occur in 3rd week following vaccination (although may occur up to 6 weeks following vaccination)