High vs. Standard Dose Flu Vaccine in Adult Stem Cell Transplant Recipients

Inclusion criteria 1. Allogeneic HSCT recipients who are 3-23 months post-transplant; 2. ≥ 18 years of age; 3. Available for duration of study; 4. Patients with stable GVHD for at least 4 weeks will be eligible (stable is defined as no major change in systemic immunosuppressive therapy for worsening GVHD; adjustment of actual dose to obtain a stable target level is acceptable). 5. Can be reached by telephone and/or electronic communication 6. Subjects must have a platelet count of ≥30,000 to receive the immunizations. Patients requiring platelet transfusions are eligible to enroll and must have a platelet count ≥30,000 within 72 hours prior to their immunization, or platelet count ≥75,000 without transfusion documented within 30 days for subjects \<12 months post- transplant and within 90 days for subjects 12-23 months post-transplant. Exclusion criteria 1. History of hypersensitivity to previous influenza vaccination or severe hypersensitivity to eggs/egg protein; 2. History of Guillain-Barre syndrome; 3. Evidence of hematologic malignancy or disease relapse post-transplant (stable mixed chimerism is permitted); 4. History of receiving current seasonal influenza vaccine post-transplant; 5. Pregnant female; 6. History of proven influenza disease after September 1, 2018 prior to enrollment; 7. Non-allogeneic (e.g. autologous) or syngeneic hematopoietic SCT recipients; 8. History of known active infection with HIV 9. History of cirrhosis 10. History of known latex hypersensitivity; 11. Subjects who have received stem cell boost or delayed donor lymphocyte infusion within 90 days of enrollment, including day of enrollment 12. Receipt of. IVIG/SCIG \<28 days prior to vaccination Criteria for temporarily delaying vaccine administration: The following conditions are temporary or self-limiting, and a subject may be included in the study once the condition has resolved, provided that the subject is otherwise eligible: 1. Fever ≥100.4ºF/38.0ºC (oral measurement), or an acute illness within 48 hours of enrollment 2. Receipt of any live vaccines within four weeks or any inactivated vaccines within two weeks prior to potential study vaccination. Note: if patients were eligible for vaccine 1, they will be eligible to receive vaccine 2 regardless of any changes on their GVHD status, unless it is deemed not medically safe to receive influenza vaccine. For subjects who were enrolled and vaccinated in 2017-18, and 2018-19, the goal is to enroll these same subjects who participated the previous influenza season year and then administer the same vaccination as the previous year. These subjects are referred to as repeaters. For example, subjects enrolled in 2017-18 year were eligible to enroll again in 2018-19 as repeaters. For subjects enrolled in 2018-19 year and received at least one vaccine, will be eligible to be enrolled as repeaters for 2019-2020 season.