The strict definition of passive immunoprophylaxis includes the administration of exogenously produced antibodies (polyclonal and monoclonal) to prevent infections in exposed individuals, inactivate bacterial toxins or "correct" hypogammaglobulinemia in immunocompromised hosts. This definition can be broadened to include modulators of the immune system. Despite advances in chemotherapy and vaccine development, suitable treatment is not currently available for many pathogens. As a result, passive immunization is an appropriate therapeutic option for many organisms.