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| Vaccination and Immunisation |
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| The principle of vaccination or immunisation is based on the property of 'memory' of the immune system. A vaccine is always given before the occurrence of the disease. |
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| A vaccine is defined as an inoculation containing germs in dead, weakened or virulent form or modified toxins which when injected inside the body, stimulates the defensive system of the body to produce antibodies. This creates an immunity inside the body of an organism against that particular disease. |
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| The process of inoculation of a vaccine into the body of an organism is called Vaccination. |
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| Vaccines are available against the diseases like typhoid, tuberculosis, tetanus, cholera, small pox, diphtheria, polio, measles, whooping cough etc. |
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| However, no vaccines are yet available for diseases like malaria, trypanosomiasis, AIDs etc. |
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| History |
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| The process of vaccination was first developed by Dr. Edward Jenner in 1796 A.D. The word 'Vaccine' who derived by him from the Latin word 'Vacca' meaning cow. He found out that the cow once attacked by a milder disease, namely cow pox, were immune to the disease small pox. This English physician, in his land mark experiment in 1796, scratched the skin of a boy to introduce into his body, the fluid from a sore of a milk maid who was suffering from cow pox. When the boy was later exposed to small pox, he showed resistance to the disease. The concept of vaccination thus evolved. |
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| Louis Pasteur, a French scientist, injected aged culture of cholera bacteria into healthy chicken. Such an aged culture was too weak to cause disease in the chicken. When fresh culture of fowl, cholera bacteria was injected into those chicken the disease did not manifest because those chicken had become immune to fowl cholera. But if fresh culture of cholera bacteria was injected to normal chicken, the disease occurred in them and the chicken died. Based on this observation, Pasteur developed a vaccine against rabies in 1885. By the end of 1920s many vaccines were available for various diseases. |
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| In vaccination, a vaccine, containing an antigen, is inoculated inside the body of an organism. Antigens, once inside the body, stimulate the body's defensive mechanism to produce anti bodies. This is primary immune response and the memory B and T cells are generated. When the vaccinated person is attacked by the same pathogen, the memory cells recognise the antigen quickly and control the invaders by producing a large number of lymphocytes and antibodies. These fight against the antigen, thus protecting the organism against that disease. The body becomes immune to that disease. |
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| The immunity developed by the body against a disease (after vaccination), may be for a short period of time, when it is said to be temporary, or may last throughout life, when it is said to be permanent. |
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| Example: |
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| Temporary immunity: Cholera Vaccine, where immunity lasts for about 6 months. |
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| Permanent immunity: Small pox vaccine, where immunity lasts throughout life. |
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| Recent advances in the development of vaccines: |
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| In recent years biotechnological techniques are implemented in the development of vaccines. |
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| Biotechnology uses these three methods for the development of vaccines. |
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| 1) Monoclonal antibodies are pure, proteinacious, antigen - specific bodies developed outside the body from clonal cultures of hybrid cells. These monoclonal antibodies have been used in immunopurification of specific antigen from a mixture of very similar antigens. This purified antigen is used for developing vaccine against a pathogen. |
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| 2) Antigen producing genes are isolated and cloned in micro-organisms using recombinant DNA technology. The antigens obtained can then be isolated from the microbes and used for the purification of vaccines. |
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| Hepatitis B vaccine is produced by this method. |
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| 3) Short peptide chains, formed of specific aminoacids sequence induces immunogenic response. They are used in preparing vaccines. |
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| Important Vaccines for Babies and Children |
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