Immunity acquired through vaccination is active immunity because it involves the deliberate exposure to an antigen, prompting the body's immune system to produce its own antibodies and memory cells. This process enables long-lasting protection against specific pathogens. Unlike passive immunity, which is obtained by receiving pre-formed antibodies, active immunity requires the host's immune response to generate immunity. Vaccination mimics natural infection without causing disease, leading to immune memory that enhances future response to the pathogen.

Reference: Immunology, K. Murphy, 9th Edition.