Aims of immunisation

• Prevent onset of disease (primary prevention) - pre-exposure in most circumstances e.g. childhood immunisation schedule, travel vaccines, occupational vaccines
• Interrupt transmission
• Alter course of infection/disease to prevent or limit consequences (secondary prevention) - immunoglobulin e.g. hep B, rabies, varicella zoster

Types of immunity

Active immunity

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

Passive immunity

• 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

Advantages of artificial passive immunity

• Rapid action
• Post-exposure
• Can attenuate illness
• Outbreak control
• Can be used if contraindication to active vaccination

Disadvantages of artificial passive immunity

• Short-term protection