RecruitingPhase 2Drug trialCMV-TCIP Directed Letermovir Prophylaxis After Allo-SCTThis is a phase 2, prospective cohort clinical trial evaluating the utilization of CMV T Cell Immunity Panel (CMV-TCIP) assay to guide the duration of primary CMV prophylaxis in CMV-seropositive recipients of allogeneic stem cell transplant or recipients receiving a stem cell graft from a CMV serology positive donor.