Question

Active immunity is not acquired by which of the following?

• A. After clinical infection.
• B. After administration of an antibody-containing preparation.
• C. After subclinical or inapparent infection.
• D. After immunization with an antigen which may be a live attenuated vaccine or toxoid.

Hint:

The key to distinguishing active vs. passive immunity is to ask: "Did the person's own body *actively* make the antibodies?" If yes, it's active. If they were given antibodies *passively*, it's passive.

Answer 1

The Correct Option is B

Step 1: Define Active and Passive Immunity. Step 1:

Active Immunity: The body generates its own antibodies in response to an antigen (foreign substance). It's long-lasting but takes time to develop.
Passive Immunity: Antibodies are received from an external source. It provides immediate, temporary protection.
Step 2: Classify the options.
Step 2:

(A) After clinical infection: The body encounters the pathogen (antigen) and produces its own antibodies. This is Natural Active Immunity.
(B) After administration of an antibody-containing preparation: The person receives pre-made antibodies (e.g., immunoglobulin). The body doesn't produce its own. This is Artificial Passive Immunity.
(C) After subclinical infection: Similar to clinical infection; the body is exposed to the antigen and produces antibodies, but without symptoms. This is Natural Active Immunity.
(D) After immunization with a vaccine/toxoid: The body is exposed to a harmless form of the antigen and produces its own antibodies. This is Artificial Active Immunity.
Step 3: Identify the method that does not lead to active immunity.
Step 3: Receiving an antibody-containing preparation provides passive, not active, immunity.