An Immunity is the power an animal has to resist and/or overcome an infection to which most of its species are susceptible. Active Immunity is due to the presence of antibodies formed by an animal in response to previous exposure to the disease or through live or modified-live vaccines. Passive Immunity is produced by giving the animal preformed or synthetic antibodies as with killed vaccines.

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Other /More definition:
An Immunity is the power an animal has to resist and/or overcome an infection to which most of its species are susceptible. Active Immunity is due to the presence of antibodies formed by an animal in response to previous exposure to the disease or through live or modified-live vaccines. Passive Immunity is produced by giving the animal preformed or synthetic antibodies as with killed vaccines.