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How does passive immunization differ from vaccination?

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Diagram of an antibody molecule showing two identical light chains and two identical heavy chains joined by disulfide bonds in a Y-shaped structure, with labeled regions for antigen binding and effector function. — antibody The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region.

Passive immunization and vaccination differ primarily in how the body acquires immunity and the duration of the protection provided.

Passive immunization involves the direct administration of pre-formed antibodies to an individual from an external source, such as through immune serum injections or natural transfer from mother to fetus. Because the recipient's own immune system is not stimulated to produce these antibodies, the protection is immediate but temporary, as the foreign antibodies are eventually eliminated from the body.123

Vaccination is a form of active immunization that introduces antigens—such as weakened or inactivated organisms—to stimulate the individual’s own immune system. This process triggers the body to generate its own antibodies and establishes immunologic memory. Consequently, vaccination typically provides long-lasting, sometimes permanent, protection and allows the immune system to respond more rapidly and effectively upon future exposure to the pathogen.324