Immunity

- Definition: A vaccine is a biological preparation that provides active immunity against specific diseases.
- Principle: Vaccines work by stimulating the immune system to produce antibodies against the disease-causing agent without causing the disease itself. This enables the body to fight the actual pathogen in the future.

Situations where a medical doctor would recommend injection of pre-formed antibodies (antitoxins):
1. Tetanus infection:
- A doctor may recommend the injection of tetanus antitoxin when a person is injured with a contaminated object or is exposed to tetanus-causing bacteria. Since the body has not yet produced antibodies to the toxin, the immediate administration of pre-formed antibodies can neutralize the tetanus toxin and prevent infection.
2. Snakebite (venom):
- If a person is bitten by a venomous snake, the doctor may administer snake antivenom (which contains pre-formed antibodies against the snake's venom). This is done to neutralize the venom before it can spread and cause severe harm to the body.