Immunity conferred by recovering from an infectious disease such as chickenpox is called active immunity. In passive immunity antibodies transferred from one individual to another.
The best medicine to treat snake bite is an antivenin or antivenom serum which provide artificially acquired passive immunity. An antivenin is prepared by injecting a horse with gradually increasing doses of a snake venom, untill the horse become fully immunised. Blood serum of horse is collected and preserved.