immunization

immunization A vaccination that works by stimulating the immune system of the body to fight disease. A healthy immune system is able to recognize invading bacteria and viruses, and it produces 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 antibodies against the whole bacteria. The effectiveness of immunizations can be improved by periodic repeat injections, called boosters. For information about specific immunizations, see the name of the disease (for examples, DTP immunization, hepatitis B immunization, polio immunization).