Question

Describe the principle of immunization in brief. Add a note on passive immunization.

Hint:

Active immunization = vaccine-induced, long-term. Passive immunization = ready-made antibodies, immediate but short-term.

Answer 1

Step 1: Principle of immunization.
\[\begin{array}{rl} \bullet & \text{Immunization is based on the principle of "memory" of the immune system.} \\ \bullet & \text{When a person is exposed to antigens (in a vaccine), the immune system produces primary response and also retains memory cells.} \\ \bullet & \text{On subsequent exposure to the same antigen, the body produces a quick and stronger secondary immune response, preventing the disease.} \\ \bullet & \text{Vaccines may be prepared from inactivated pathogens, attenuated pathogens, or microbial products.} \\ \bullet & \text{Examples: BCG (tuberculosis), OPV (polio), Hepatitis B vaccine.} \\ \end{array}\]

Step 2: Passive immunization.
\[\begin{array}{rl} \bullet & \text{Passive immunization involves the direct introduction of pre-formed antibodies into the body.} \\ \bullet & \text{It gives immediate but short-lived protection.} \\ \bullet & \text{Used in cases of life-threatening infections, like tetanus, diphtheria, and snake-bite.} \\ \bullet & \text{Example: Injection of anti-tetanus serum, anti-rabies serum.} \\ \end{array}\]

Step 3: Conclusion.
Immunization is a vital tool in preventive medicine, and while active immunization provides long-term protection, passive immunization is useful in emergencies.