Immunity is the ability of microorganisms to resist infection by protecting against disease causing microorganisms. When the body has enough antibodies (or can produce quickly enough) to fight infection.

  • Active Natural: Exposed to foreign antigen by getting the disease – immune system is activated – body produces memory cells, making the body immune to the same disease in the future
  • Active artificial: Vaccination – Injection of dead and weakened disease organisms, toxins or antigen fragments means the body is exposed to the antigen and produces memory cells – develops immunological memory – if exposed to same disease again, antibodies are quickly released
  • Passive natural: A mother’s antibodies across the placenta or through breast milk – these antibodies protect the baby against any pathogens the mother has encountered – short-term as antibodies are broken down within a few days
  • Passive artificial: Antibodies are formed in one individual, injected with antibodies that provide immediate protection against the invading pathogen they are specific for – then gradually broke down and not replaced


Active = body produces its own antibodies – catching a disease – long-term

Passive = body receives ready made antibodies – vaccination – short-term



Substance that stimulates immunity without getting the disease – it is non virulent. Antigens come from weakened, dead or fragmented pathogens. This stimulates memory cells to develop – ready to destroy the real pathogen if encountered.

Vaccinations need to be affordable, available, have few side effects and be able to provide herd immunity.

Types of vaccination: pathogenic, antigens, harmless toxins, live MOs

Vaccinations don’t eliminate disease if:

  • Immune system is defective
  • Disease develops before immunity is built
  • Mutations arise (antigenic variability)
  • If the pathogen hides/conceals itself
  • May varieties of a pathogen
  • Individuals don’t receive vaccination

Advantages of vaccination:

  • Protects against disease
  • Herd immunity
  • Most common vaccinations are relatively cheap

Disadvantages of vaccination:

  • Some may suffer from allergic reactions
  • Minority of children become severely ill/death
  • Linked to a rise in asthma and allergies

Ring vaccination: used for new cases of disease. Vaccinates people in immediate vicinity of the disease – e.g. surrounding people, can control livestock disease