Immunisation

• Infectious diseases are capable of being transmitted (spread) from

  one person to another by direct or indirect contact.
• Direct physical contact could be by shaking hands or sexual contact.
• Water and food could be contaminated with microorganisms from an infected person.
• Body fluids could contain pathogens which may be passed on to another person during kissing (exchange of saliva) or sexual intercourse (seminal fluids).
• Inhaled air could contain droplets carrying pathogens from a person who has sneezed or coughed.
• Vector organisms such as mosquitos can carry malaria or yellow fever pathogens.
• Infectious diseases are caused by pathogens such as viruses,

  bacteria, fungi, protozoa and multicellular parasites. A pathogen is a bacterium, virus, or other microorganism that can cause disease.
• Active immunity can be developed by vaccinations with antigens

  from infectious pathogens. This creates immunological memory.
• Vaccinations are made from a dead or weakened form of the

  pathogen, from part of a pathogen or from a pathogens

  inactivated toxin. They are injected into the body to act as an

  antigen. An adjuvant is a substance which is added to the vaccine making it more effective, so enhancing the immune response.
• The advantage of using vaccines from altered pathogens is that

  the body produces B and T cells but does not develop the disease.
• Some of the B and T cells will remain in the body as memory cells

  which will initiate a secondary response if the person is exposed

  to the disease-causing pathogen at a later date.
• We say that the person has acquired active immunity by artificial means.