<prompt> Active immunity is not acquired by -InfectionVaccinationImmunoglobulin transferSub-clinical infection  <response>: Active immunity is the resistance developed by an individual as a result of antigenic stimulus. Naturally acquired active immunity occurs when a person is exposed to a live pathogen, clinical subclinical and develops a primary immune response, which leads to immunological memory. Aificially acquired active immunity can be induced by a vaccine, a substance that contains antigen. A vaccine stimulates a primary response against the antigen without causing symptoms of the disease. Ref: Ananthanarayan Panikers textbook of microbiology 9th edition pg.no. : 81-84 