Definition of Active immunity

Active immunity: The production of antibodies against a specific agent by the immune system. Active immunity can be acquired in two ways:

• by contracting an infectious disease -- such as, for example, chickenpox; or
• by receiving a vaccination usually pe-- such as, for example, against polio.

Active immunity is permanent. The individual is protected from the disease all their life. See also: Passive immunity. Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=2130
Last Editorial Review: 9/13/2003