Deliberate stimulation of the host's immune response. ACTIVE IMMUNIZATION involves administration of ANTIGENS or IMMUNOLOGIC ADJUVANTS. PASSIVE IMMUNIZATION involves administration of IMMUNE SERA or LYMPHOCYTES or their extracts (e.g., transfer factor, immune RNA) or transplantation of immunocompetent cell producing tissue (thymus or bone marrow).

Synonyms: Immunization, Immunostimulation, Variolations, Immunological Sensitizations, Stimulation, Immunological, Sensitization, Immunologic, Sensitization, Immunological, Immunological Stimulations, Stimulation, Immunologic, Immunological Sensitization, Immunologic Stimulation, Immunizations, Sensitizations, Immunological, Immunological Stimulation, Stimulations, Immunological, Immunologic Sensitization, Variolation