Inclusion Criteria:  Undergone allogeneic, autologous, or cord blood stem cell transplantation at least 21 days prior to randomization and demonstrated engraftment with an absolute neutrophil count >500/µL Detection of at least 1 target virus of interest (ie, RSV, influenza, hMPV, and/or PIV) Has an HLA type matching with at least 1 suitably matched ALVR106 cell line  Diagnosis of URTI, defined as all of the following:  New onset of at least 1 of the following respiratory symptoms for ≤4 days prior to screening: nasal congestion, runny nose, cough, or sore throat, or worsening of 1 of these chronic respiratory symptoms (associated with a previously existing diagnosis, eg, chronic rhinorrhea, seasonal allergies, or chronic lung disease). Absence of significant hypoxia (ie, oxygen saturation ≥92% on room air) at screening and randomization, or need for exogenous oxygen. Absence of abnormalities consistent with LRTI on a chest X-ray and/or CT scan as assessed by the local radiologist.  High-risk patients following HCT, who may have ANY of the following:  Lymphocyte count <180/mm3 <100 days following HCT CD4 T cell count <50/mm3 within 90 days following HCT Ex vivo graft manipulation resulting in T cell depletion Haploidentical transplantation Undergone cord blood stem cell transplantation Unrelated donor with at least one mismatch at one of the following four HLA-gene loci: HLA-A, -B, -C and -DRB1 Received T-cell depletion or alemtuzumab (Campath®) Considered to be high risk for respiratory disease  Exclusion Criteria:  Ongoing therapy with high-dose systemic corticosteroids (ie, prednisone equivalent dose >0.5 mg/kg/day) Prior therapy with antithymocyte globulin, alemtuzumab (Campath-1H), or other immunosuppressive T cell-targeted monoclonal antibodies Proven or suspected infection by novel coronavirus disease 2019 (COVID-19) within 28 days Evidence of Grade >2 acute graft versus host disease (GVHD) Known or presumed non-viral pneumonia or sinusitis secondary to any organism. Receipt of another investigational antiviral treatment during the study or within 28 days prior to randomization or study treatment administration Donor lymphocyte infusion or other T cell therapies performed <21 days prior to randomization