What occurs during active immunity?

Active immunity occurs when the immune system is exposed to a specific antigen, leading to a robust immune response. This can happen naturally through infection or artificially through vaccination. When the immune system encounters the antigen, it generates specific antibodies and activates various immune cells, creating memory cells that help protect the body against future infections by the same pathogen.

The active process of the immune response means that the body is actively involved in producing its own antibodies, making it distinct from passive immunity, where antibodies are received from another source, such as maternal antibodies passed to an infant. Additionally, while vaccines can be inactivated or live, the key aspect of active immunity is the engagement of the immune system itself rather than the type of vaccine used. Active immunity does not guarantee lifelong immunity without further exposures; it typically depends on the nature of the antigen and the individual's immune response.