Immunisation

Question 1

Aims of immunisation?

Answer 1

Control of communicable disease
Prevent onset of disease (primary prevention) - pre-exposure in most circumstances e.g. childhood immunisation schedule, travel vaccines, occupational vaccines

Alter course of infection/disease to prevent or limit consequences (Secondary prevention)
Immunoglobulin - e.g. Hep B, Rabies, Varicella zoster

Interrupt chains of transmission

Question 2

Immunological mechanisms?

Answer 2

Active immunity
Passive “”
Herd “”

Question 3

Deciding what vaccines should be offered?

Answer 3

• Is there a need for it (epidemiological factors)?
  disease incidence
  disease complications
  case fatality ratio
  age distribution
  trends
• Does it work (vaccines research)?
• Other factors
  costs (health economic assessment)
  model of delivery
  acceptability
  political factors
  aim of programme

Question 4

Meningococcal disease?

Answer 4

due to Neisseria meningitidis
Meningitis (35%)
Septicaemia (30%)
Men&Sept (20%)

Question 5

What is active immunity?

Answer 5

• Protection that is produced by an individual’s own immune system via B and T cells
• Usually long-lasting

Question 6

What is Passive immunity?

Answer 6

transfer of pre-formed antibodies (Immunoglobulins)
- Natural passive immunity: mother to unborn baby via placenta
- Last up to 1 year
- Some antigens (e.g. measles) but not others (e.g. pertussis, as CM immunity important)
- Artificial passive immunity: from another person or animal e.g. human IgG for hep B, anti-toxin for diptheria
- Antibodies from blood donors
- Human normal Ig
- Specific Ig

Question 7

Main points about Passive VS Active immunity?

Answer 7

Question 8

Herd immunity?

Answer 8

(population protection)
- Protect unvaccinated individuals, by having a sufficiently large proportion of the population vaccinated
- Vaccinated individuals stop transmission of organism
- Proportion required to be immune derived mathematically, dependent on R0 which is based on:
- Transmissibility and infectiousness of organism
- Social mixing in population

Question 9

How new vaccines are investigated?

Answer 9

• Phase I: is it safe, is it immunogenic
• Phase II: how reactogenic is it, dosage, how it compares with current vaccines
• Phase III: efficacy, any rarer reactions/safety issues
• Phase IV: post-marketing surveillance - yellow card scheme (passive reporting, suspected adverse drug reactions)

Question 10

Types of vaccines?

Answer 10

Live virus vaccines

• Attenuated organism, replicates in host e.g. OPV, MMR, rotavirus

Inactivated vaccines

• Suspensions of killed organisms e.g. whole-cell pertussis (whooping cough), whole-cell typhoid
• Subunit vaccines
  
  • Toxoids e.g. diphtheria toxoid, tetanus toxoid, pertussis toxoid
  • Polysaccharides e.g. pneumococcal, typhoid (Vi)
• Conjugate vaccines - polysaccharide attached to immunogenic proteins e.g. Hib, MenC