Immunization

Vaccination. Immunizations work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Immunizations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed. To immunize against bacterial diseases, it is generally possible to use only a small portion of the dead bacteria to stimulate the formation of antibodies against the whole bacteria. In addition to the initial immunization process, it has been found that the effectiveness of immunizations can be improved by periodic repeat injections or "boosters." Also see Immunizations (in the plural) and

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Protection of susceptible individuals from communicable diseases by administration of a living modified agent ( e.g., yellow fever vaccine), a suspension of killed organisms ( e.g., pertussis vaccine), or an inactivated toxin ( e.g., tetanus). SEE ALSO: vaccination, allergization.

- active i. the production of active immunity.

- passive i. the production of passive immunity.

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im·mu·ni·za·tion also Brit im·mu·ni·sa·tion .im-yə-nə-'zā-shən n the creation of immunity usu. against a particular disease esp treatment (as by vaccination) of an organism for the purpose of making it immune to a particular pathogen <\immunization against polio>

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n.

the production of immunity by artificial means. Passive immunity, which is temporary, may be conferred by the injection of an antiserum, but the production of active immunity calls for the use of treated antigens, to stimulate the body to produce its own antibodies: this is the procedure of vaccination (also called inoculation). The material used for immunization (the vaccine) may consist of live bacteria or viruses so treated that they are harmless while remaining antigenic or completely dead organisms or their products (e.g. toxins) chemically or physically altered to produce the same effect.

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im·mu·ni·za·tion (im″u-nĭ-zaґshən) the induction of immunity; see active i. and passive i.