Florida Biology EOC Practice Test

How long does passive immunity usually last?

1. A few weeks

2. It is permanent

3. Several years

4. Up to a lifetime

The correct answer is: A few weeks

Passive immunity typically lasts for a short duration because it involves the transfer of antibodies from another source rather than the individual's own immune response. This type of immunity is usually acquired through maternal antibodies passed to a newborn, either through the placenta or breast milk. The presence of these antibodies helps to provide immediate protection against certain pathogens, but since the body does not produce its own antibodies in response, this immunity diminishes relatively quickly. This duration of a few weeks is typical for passive immunity, as the transferred antibodies gradually degrade and the protective effect wanes. The other options suggest durations that are not consistent with the nature of passive immunity—either indicating a permanent state, which is not the case as it does not contribute to long-term immunological memory, or suggesting a lifespan of several years or up to a lifetime, which applies more to active immunity, where the immune system has had time to produce its own antibodies through exposure to pathogens or vaccinations.