What is passive immunity?

Passive immunity refers to the short-term immunity that is gained through receiving antibodies from another source rather than developing them through one's own immune response. This can occur naturally, such as when a mother passes immunoglobulins to her baby either through the placenta during pregnancy or through breast milk after birth. It can also be acquired artificially by administering pre-formed antibodies, which provides immediate but temporary protection against specific pathogens.

This is distinct from active immunity, which involves the individual's immune system actively producing antibodies in response to an antigen, such as through natural infection or vaccination. The key characteristic of passive immunity is its transient nature; because the body does not produce the antibodies, the immunity usually only lasts for a few weeks to months until those antibodies degrade. Understanding this distinction is critical, especially in public health contexts, where both types of immunity have distinct implications for vaccination strategies and disease prevention.