What is Immunisation?
Now used synonymously, the terms 'vaccination' and 'immunisation' refer to inoculation with a virus or bacteria to render a person immune to certain infectious organisms and prevent subsequent disease. The organisms used in the vaccine are so modified that they are harmless to humans and yet still induce immunity.
Originally vaccination meant inocultion with vaccinia, or cowpox, as a protection against an attack of smallpox. This treatment was discovered by Edward Jenner in 1796 and a century later Louis Pasteur used the term to include all inoculations that employed germs to induce immunity. When a vaccine is introduced into the body the body's defence mechanisms react to its presence and manufacture antibodies to destroy the germs. The next time that the body encounters the same germs its defence system destroys them before they cause disease. Vaccines are now used against smallpox, tuberculosis, yellow fever, poliomyelitis and rabies. Another method of immunisation uses dead organisms, which retain their ability to produce immunity. This form of immunisation is used to prevent such diseases as influenza, measles, cholera, typhoid and whooping cough. Some diseases are caused by toxins released from the infecting organisms and in such cases immunity can be induced by inoculation with a 'toxoid', which is the toxin in a modified form.
Vaccines have been introduced as a part of a routine immunisation of children. The immunisation programme generally includes inoculations against diphtheria, tetanus, whooping cough, measles and poliomyelitis before the child commences school and rubella (German measles) for pubescent girls. Vaccinations do not confer lifelong immunity with one injection, so booster injections at regular intervals are necessary.