immunization

Process of conferring immunity to infectious disease by artificial methods, in other words making someone not liable to catch a disease. The most widely used technique is vaccination (see vaccine). Immunization is an important public health measure. If most of the population has been immunized against a particular disease, it is impossible for an epidemic to take hold.

In vaccination people can be immunized against a disease by introducing small quantities of dead or inactive forms of the disease-causing micro-organism into the body. In the vaccine are chemicals which act as antigens. These stimulate the white blood cells to produce antibodies. Antibodies are capable of binding to disease-causing bacteria, resulting in their destruction. If the body is effectively ‘warned’ about the antigen by this means, the body is then able to produce enough of the appropriate antibody whenever the living disease-causing organism enters the body. The micro-organism can then be killed before it harms the body. The person contacted by the disease will probably feel well all the time and will be unaware that he or she has been in contact with the disease. This is called active immunity.

Vaccination can be used to protect against diseases caused by viruses. It is, in fact, the best way to deal with virus diseases, because antibiotics are not effective against them. An example is the MMR vaccine used to protect children against measles, mumps, and rubella. A study of thousands of children in Finland who have had the MMR vaccine has shown that there is only a very low risk of damage being caused to a child as a result of having the vaccine. The risk is much lower than the damage caused by catching one of the diseases.

If vaccination covers a large proportion of the population at risk, a disease can become very rare, or even die out. Smallpox was eliminated in this way. The worries over MMR vaccine have reduced the numbers of children being vaccinated, which increases the risk of measles, mumps, or rubella breaking out in an epidemic.

Current research

History of vaccination Vaccination against smallpox was developed by Edward Jenner in 1796. In the late 19th century, Louis Pasteur developed vaccines against cholera, typhoid, typhus, plague, and yellow fever. In 1991, the WHO and UNICEF announced that four out of five children around the world are now immunized against six killer diseases: measles, tetanus, polio, diphtheria, whooping cough, and tuberculosis. Ten years ago this figure was only one in five children.