A method of producing artificial immunity to infectious diseases, usually involving a course of injections
Immunization is a way of boosting the body’s defences against infectious diseases. Most immunizations use a vaccine containing a tiny amount of a weakened or inactivated form of a disease-causing organism (see Vaccines and immunoglobulins). When the vaccine is introduced into your body, it stimulates your immune system to produce antibodies against the disease so that you are protected if you are exposed to the actual organism at some time in the future. Most vaccines are given by injection. For most immunizations, several injections of the vaccine are given over a period of months or years to build up adequate protection.
Most routine immunizations are given during infancy and childhood according to an immunization schedule. In addition, people who are at particular risk, because of the nature of their work or travel, may be offered extra immunizations during their adult life. Keep records of all your immunizations and those of your children in case a doctor other than your GP needs to know about your immune status.
Most immunizations are given to babies during their first year, when infectious diseases are most likely to be serious. A baby has some natural protection from antibodies that pass through the placenta during pregnancy, but this immunity wears off by about 6 months after birth. Premature babies are immunized routinely because they are at high risk of serious illness if they develop an infection.
By the time children start school, they will have completed most of their schedule of routine immunizations, although some immunizations are given during the school years (see Routine immunizations). If a child starts the schedule late, the timings of vaccinations can be adjusted so that he or she receives the full complement.
Adults sometimes need a booster dose in special circumstances. For example, you may need an extra injection against tetanus if you sustain a deep or dirty cut.
Influenza and pneumococcal pneumonia can be serious disorders, particularly in people over the age of 65 or in those who have reduced immunity because of long-term conditions such as diabetes mellitus or HIV infection and AIDS. Both children and adults in these high-risk groups are offered immunization against these diseases. You may also need to have extra immunizations if you plan to travel to a country that has a high incidence of infectious diseases, such as hepatitis or yellow fever (see Travel immunizations).
Immunizations have few side effects, although there may be some inflammation around the injection site or a mild fever. If you have any reactions to initial doses, tell your doctor so that he or she can advise you about subsequent doses. Serious side effects are extremely rare. There is no evidence that immunization with the MMR (measles, mumps, rubella) vaccine causes autism or Crohn’s disease. Research has shown that, in general, the risks to children from routine immunizations are substantially lower than the risks associated with the diseases against which they protect.
Homeopathic types of vaccine have been shown to be ineffective. If you rely on them, you could be putting yourself or your children at risk.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.