Vaccines

Question 1

Which are the live attenuated viral injections

Answer 1

VZV and MMR

VZV: Varicella Zoster virus (causes chicken pox during primary infection)

Question 2

Advantages of live attenuated vaccine

Answer 2

• Virus is able to enter cells → stimulates the activation and sensitisation of T lymphocytes → allows for cellular and humoral immunity to be triggered
• Single dose is sufficient

Question 3

What is herd immunity

Answer 3

• Immunisation of a large enough proportion of the community to prevent the spread of pathogens
• Some individuals cannot be immunised (ie those who are immunocompromised as they will not be able to mount an immune response and form immunological memory)
• Easier spread of pathogen between people → higher threshold for herd immunity
• 80-95% of population has to be immunised for herd immunity to be effective

Question 4

When are toxin based vaccines used

Answer 4

Key disease causing (virulence factor) molecule made by the pathogen is a secreted protein exotoxin

Question 5

Which type of vaccine engenders the strongest immune response

Answer 5

Live attenuated vaccine

Question 6

Disadvantages of live attenuated vaccine

Answer 6

1. Virus may revert to virulent form/retain pathogenicity
2. May result in adverse reactions
3. May not be safe for immunocompromised patients
4. Requires cold chain of transport as virus can be easily destroyed

Question 7

How does a vaccine work

Answer 7

1. Engendering immunological memory without the morbidity and pathology that is normally associated with natural infection
2. First exposure to pathogen is usually IgM, hence sometimes boosters are required in single protein antigens to engender a stronger immune response (with IgG)
   [upon second exposure]
   - Lag time to make an antibody response decreases
   - Scale of our antibody response increases
   - Form of our antibody response changes from IgM to IgG/IgA (if exposure if at mucosal sites); qualitative improvement in the affinity (specificity) of our antibody repertoire for the taget antigen (affinity maturation)

Question 8

What are adjuvants

Answer 8

• Chemical irritants/bacterial cell wall components mixed into vaccine targets
• Designed to stimulate the innate immune system → required to make a strong adaptive immune response