Which type of immunity is primarily temporary?

Passive immunity is primarily temporary because it involves the transfer of antibodies from one individual to another, rather than the host's immune system generating its own antibodies. This type of immunity can occur naturally, such as when antibodies are passed from mother to baby through breast milk or the placenta, or it can be acquired artificially through immunization with pre-formed antibodies. However, since the recipient's body did not produce these antibodies, their presence in the bloodstream is transient. Over time, these antibodies degrade and the passive immunity wanes, typically within weeks to months, depending on the type of antibodies involved.

In contrast, natural immunity results from exposure to pathogens and the subsequent establishment of immune memory, which provides lasting protection. Active immunity, whether through natural exposure or vaccination, involves the host's immune system actively engaging with an antigen to produce its own antibodies and memory cells, leading to long-term immunity. Adaptive immunity encompasses both active and passive immunity but focuses on the body's capacity to adapt its immune response to specific pathogens over a longer period. Therefore, the defining characteristic of passive immunity is its temporary nature, making it the correct choice in this context.