Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Altered immunocompetence is defined by loss or qualitative deficiency in cellular or humoral immune components that occurs as a result of a disease process or a disease therapy. Vaccines may be less effective during the period of altered immunocompetence. HSCT is often associated with a loss or diminution of protective immunity against pathogens targeted by childhood immunizations. As a result, there has been interest in vaccinating patients in...