- Injection of a killed microbe in order to stimulate the immune system against the microbe, thereby preventing disease. Vaccinations, or 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 only immunize against bacterial diseases, it is generally possible to use 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 Vaccines (in the plural) and Vaccine of a specific type (such Vaccine, Polio).
* * *The act of administering a vaccine.
* * *vac·ci·na·tion .vak-sə-'nā-shən n1) the introduction into humans or domestic animals of microorganisms that have previously been treated to make them harmless for the purpose of inducing the development of immunity <oral \vaccination> <\vaccination against smallpox> <\vaccination for whooping cough>2) the scar left by vaccinating
* * *n.a means of producing immunity to a disease by using a vaccine, or a special preparation of antigenic material, to stimulate the formation of appropriate antibodies. The name was applied originally only to treatment with vaccinia (cowpox) virus, which gives protection not only against cowpox itself but also against the related smallpox. However, it is now used synonymously with inoculation as a method of immunization against any disease. Vaccination is often carried out in two or three stages, as separate doses are less likely to cause unpleasant side-effects. A vaccine is usually given by injection but may be introduced into the skin through light scratches; for some diseases (such as polio), oral vaccines are available.
* * *vac·ci·na·tion (vak″sĭ-naґshən) [L. vacca cow] the introduction of vaccine into the body for the purpose of inducing immunity. Coined originally to apply to the injection of smallpox vaccine, the term has come to mean any immunizing procedure in which vaccine is injected.
Medical dictionary. 2011.