The human environment provide him with all his basic needs for survival-air, water, food and shelter
But also provide him with exposure to infective agent’s virus, bacteria, etc which many make it impossible for him to complete his normal life span, unless he is adequately prepared to withstand these organisms. To be able to withstand those infective organisms, a child must have within his body substances called antibodies which attack any of these disease causing organisms once they enter his body. However these antibodies are very specific and the antibodies against organism A are usually not effective against organism B. The more of these infective agent one is expose to, the more the body tries to develop the appropriate antibodies against them. When a man has developed appropriate antibodies against a particular disease he is said to be immune to that disease.
There are two principal ways of acquiring immunity to a disease through passive immunization, or through active immunization. In passive immunization, already formed antibodies are provided for the person either through blood of the mother to the baby during pregnancy, through immunoglobulins.
In the active type of immunization, the person either gets the mild form of the disease and they develops the appropriate antibodies himself or he is given a modified form of the infective agent which enable him to form the appropriate antibodies to the organisms but is not sufficient to cause the disease. It is the process of giving somebody these modified infective agents that is called immunization.
While immunization may be performed anytime in one’s life depending on the prevalence of the disease or if one has to travel or if there is an epidemic. The ones that are done in early life called childhood immunization are best given in before the child is one year old but certainly not after two y ears. By the age of two, it is known that most children would have been exposed to the infective organisms of the major killer disease of childhood and would have either had the disease or have developed the appropriate antibodies to them. However during immunisation blitz,the age bracket targeted is 9mths to 59mths.
The major killer disease of childhood in this environment for which there is effective immunization are Tuberculosis, Polio-myelitis, Diptheria, Tetanus, Measles and Whooping cough. It is because the weapon to fight these diseases are readily and cheaply available that the current efforts of various governments, both federal and states, to get every child immunized, should be supported by taking the children to the nearest immunization centers to get them immunized. It is equally important to stress that immunization is not complete until the requested number of doses are taken
For BCG (the immunizing agent againstTuberculosis) and measles. it is one dose. For Polio and Triple Antigen (the immunization agent against Diptheria, Tetanus and Whooping tough) it is 3 doses.
These six killer diseases are well known to the experienced mothers because they are still quite common, although the frequency at which they are seen is now decreasing – thanks to the Expanded Program me on Immunization PI.
Apart from childhood immunization there may still be need later in life to get immunized against other diseases. Yellow fever immunization is one example of immunization that may be needed in adult life. Similarly, cholera immunization for travellers to certain parts of the world. In some part of this country- the northern parts particularly cerebra spinal meningitis still occurs in epidemic proportions and active immunization of both children and adults are usually carried out to protect the people and curtain the spread of the dreadful disease.
There are also many other diseases against which effective vaccines are available and the process of immunization usually does not require more than one shot of injection.
Perhaps the most important advantage of the immunization process is that it can be use d not only to halt the transmission cycle of a disease but to eradicate it completely. In many party of world there is no more indigenous measles and the few of measles still seen are from immigrants the classical example of the use of immunization to eradicate a disease is global eradication of small pox in 1978. Since 1978 when small pox was declared eradicated by WHO, no proven cases of the disease have been seen , most of the cases reported as small pox since that time are usually those of other diseases which look like small pox especially chicken pox . Even malaria, the single most important cause of morbidity and mortality in our environment is soon to be amenable to immunization. The malaria vaccine is now at the field trial stage and one can confidently say that within the next decades, the vaccine will be available in the market. In a related situation the vaccine against leprosy is said to be at clinical trial stage that vaccine may even be on the market much earlier than that of malaria.