The defense achieved through the production of antibodies in the body is called active immunity. Active defense is of two types. These are-
(i) Natural Active Defense: Infection occurs when humans are involuntarily exposed to microbes. All these germs are eradicated by naturally acquired abilities.
(ii) Artificial active immunity: Humans acquire this immunity through inoculation or vaccine. For example, DDP vaccine is taken for diphtheria, tetanus vaccine for scurvy and pertussis vaccine for whooping cough.