When we catch a disease naturally, we usually produce antibodies to the organism that causes it. Antibodies are proteins in the blood which remember the organism which caused the disease, can recognise it and inactivate it when we come into contact with it again. Without us actually experiencing the disease, vaccines teach our body’s immune system to produce antibodies and identify certain potentially infective organisms even though we have never come into contact with them.

Vaccines take various forms:

  • Killed or inactivated vaccines are produced by chemically killing or inactivating bacteria or viruses. The now harmless bacteria or viruses, when injected, stimulate the body to produce antibodies, without the individual having to suffer the disease.
  • Live vaccines are produced by weakening the ability of the organism to produce disease while retaining its ability to produce immunity.
  • Vaccines may be made by identifying and purifying those fragments of the disease-producing organisms that are most import in stimulating antibodies. These fragments may be substances found on the surface of the organism which the immune system recognises or others such as the toxins produced by some bacteria.
  • These fragments can also be produced by modifying the genetic material of a totally different cell so that this cell produces copies of these fragments, which can then be purified and used to make a vaccine.

Once adminstered the user is usually protected for life or until a new strain comesabout.

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