IMMUNISATION is the most effective preventative measure against infectious diseases. Some vaccines offer lifelong immunity. In other cases, booster shots are needed.
Serious side effects from vaccines are rare, and much less common than serious effects of the disease. Some diseases, such as poliomyelitis or diphtheria, can be so destructive that the infected person may suffer lifelong complications or even die.How vaccines work
The human immune system is a collection of special cells and chemicals that fight infection. The human body can gain immunity against certain diseases either naturally (by being infected and recovering, or coming into contact with, the illness) or through immunisation. Vaccines work by introducing a modified version of a disease-causing microbe (germ) to the immune system, either by injection or within a small drink. Depending on the disease, the vaccine could be a weakened or dead germ or a section of a germ (for example, its protein wall). In other cases, where disease is caused by toxins produced by bacteria, the vaccine contains the weakened toxin.
The immune system responds to the weakened, partial or dead germ as if it was a fully-fledged germ and makes antibodies to destroy it. These antibodies are made without the person getting sick. Later, some of these antibodies remain ‘on patrol’ in the bloodstream and can increase quickly if the germ is encountered. This means that the key to defeating that particular disease is stored long term. This is called ‘immunological memory’. Vaccines mimic natural immunity
A person’s natural immunity is like a library and contains information on every germ ever defeated by their immune system. If the person encounters the real disease-causing germ in the future, their immune system will know how to defeat it, often before the person experiences any symptoms of illness. This explains why (in most cases) diseases such as mumps and rubella (German measles) are only caught once, even though exposure to the virus may be repeated throughout life.History of immunisation
Immunisation techniques were pioneered over 200 years ago, when smallpox was a feared and deadly disease. An eighteenth century doctor named Edward Jenner noted that farm labourers who contracted the mild disease cowpox were immune to smallpox. Jenner guessed that the germ responsible for cowpox was similar enough to the smallpox microbe to ‘train’ the immune system to defeat both diseases. He was right. Immunisation today relies on broadly similar principles.No vaccine is completely effective
Out of 100 people immunised against a particular disease, about five to 15 will still catch the disease if exposed to it. This may be because their immune systems didn’t respond to the vaccine and failed to make antibodies, or the vaccine may not have been stored correctly at the clinic. However on the other hand, if 100 people who have never had measles or have never been immunised against it were exposed to the measles germ, almost every single one of them would catch it. Immunisation greatly reduces the risk of catching a disease, which in turn reduces the risk of complications.Comparing the risks
The safety of vaccines has been questioned from time to time. Like any other medicine, vaccines carry a small degree of risk, but serious side effects are very rare. This must be weighed against the risk of the disease. For example, the risk of encephalitis (inflammation of the brain) from the measles, mumps, rubella (MMR) vaccine is thought to be just one in a million immunisations. However, according to some estimates, the risk of encephalitis from catching the mumps virus is one in 200.People who work with children
If you work with children in jobs such as teaching or child care centres, you need to remember that you are at an increased risk of catching and passing on infectious diseases. Stay up to date with all necessary vaccinations to protect yourself and the children you are in regular contact with. Some diseases cause only a mild illness in adults but can be very serious for young children. For example, whooping cough (pertussis) can be deadly for young babies.