1 History of AIDS or being HIV positive 2 Hepatitis B or C infection 3 History of intravenous drug use 4 Blood cancer (leukemia, lymphoma, Hodgkin's disease) 5 Chronic kidney disease requiring dialysis 6 Heart disease with ongoing symptoms 7 History of stroke or cerebrovascular disease 8 Chronic lung disease (severe asthma, COPD) 9 Insulin-dependent diabetes mellitus 10 History of organ transplantation 11 Chronic liver disease or cirrhosis 12 History of Creutzfeldt-Jakob Disease (CJD) 13 Bleeding disorders (hemophilia, von Willebrand disease) 14 History of epilepsy or recurrent seizures 15 History of babesiosis or Chagas disease 16 Multiple sclerosis or other autoimmune diseases 17 History of tissue or dura mater transplant 18 Chronic mental illness with ongoing treatment 19 History of malaria in endemic areas 20 Chronic inflammatory conditions (severe arthritis) 21 History of human growth hormone treatment 22 Chronic use of immunosuppressive medications 23 History of tuberculosis with lung complications 24 Any condition deemed unsafe by medical staff