A Level Biology Practice Exam

Passive immunity refers to the short-term immune protection that is conferred through the transfer of antibodies from one individual to another. This can occur naturally, such as when maternal antibodies are passed to a baby through the placenta during pregnancy or through breast milk during breastfeeding. It can also be achieved artificially, for example, through the administration of antibody-rich serum or immunoglobulin preparations for immediate, short-term protection against specific infections.

While natural infection and vaccination result in active immunity—where the body is exposed to a pathogen or a vaccine and produces its own antibodies—passive immunity does not involve the host's immune system generating a response; rather, it temporarily acquires the ability to fight off infections through antibodies that were produced by another organism. Therefore, option C captures the essence of what passive immunity entails by emphasizing the transfer of pre-formed antibodies rather than the body's own active response to infections.