What Is Immunization?

Immunization protects against infection without the risks associated with the disease. A vaccine triggers active immunity by stimulating development of antibodies by a mechanism that mimics the response to infection. This process takes time, so protection does not develop immediately. The protection that results may be lifelong or may be limited in duration, necessitating booster doses of the vaccine. Passive immunity results when preformed antibodies are administered that provide immediate but relatively short-lived protection from infection. Examples of passive immunity include nonspecific immunoglobulin (“gamma globulin”), intravenous immune globulin (IVIG), specific immune globulin (e.g., tetanus immunoglobulin), and antitoxin (equine diphtheria antitoxin). When preformed antibodies are administered to an unimmunized individual to manage an acute exposure, subsequent administration of a vaccine is needed (if one is available) to trigger development of active immunity and provide lasting protection against disease.

What Is a Vaccine?

Vaccine is a generic term that refers to any immunobiologic agent administered as part of a program of active immunization. Most vaccines are suspensions made from attenuated (live) or killed bacteria and viruses or from specific components of those organisms. A toxoid is a bacterial protein (toxin) that has been rendered biologically inactive and is used as a vaccine to stimulate the active development of antibody (antitoxin). Tetanus toxoid is the major example.

What Immunizations Are Currently Recommended?

Immunization recommendations are reviewed and updated yearly, and new vaccines and combinations of vaccines are added with some regularity. Immunizations recommended in the United States are listed by the Centers for Disease Control and Prevention (www.cdc.gov/vaccines) and the American Academy of Pediatrics (www.aap.org/healthtopics/immunizations.cfm). Table 12-1 lists currently recommended vaccines. Each state sets its own standards for required immunizations. Table 12-2 lists sources of reliable information.

Table 12-1 Immunizations (2007)

Table 12-2 Sources for Information on Immunizations