Prognostic factors for the development of lower respiratory tract infection after influenza virus infection in allogeneic hematopoietic stem cell transplantation recipients: A Kanto Study Group for Cell Therapy multicenter analysis

•Lower respiratory tract infection (LRTI) is a feared complication of influenza virus infection in allogeneic hematopoietic stem cell transplantation recipients.•The risk factors and demographics of LRTI are discussed in a large cohort.•Early neuraminidase inhibitor therapy reduces the risk of progression to LRTI in these patients. Influenza virus infection (IVI) occasionally causes lower respiratory tract infection (LRTI) in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Although the progression to LRTI entails a high mortality, the role of early antiviral therapy for its prevention has not been fully elucidated. This was a multicenter retrospective study using an additional questionnaire. Allo-HSCT recipients who developed IVI between 2012 and 2020 were included. A total of 278 cases of IVI after allo-HSCT were identified from 15 institutions. The median patient age was 49 years, and the median time from allo-HSCT to IVI was 918 days. Neuraminidase inhibitors were administered within 48 hours of symptom onset (early neuraminidase inhibitor [NAI]) in 199 (76.9%) patients. Subsequently, 36 (12.3%) patients developed LRTI. On the multivariate analysis, age ≥50 years (hazard ratio [HR], 2.16; 95% confidence interval [CI], 1.02-4.58) and moderate to severe chronic graft-versus-host disease (HR, 2.28; 95% CI, 1.14-4.58) were significantly associated with progression to LRTI, whereas early NAI suppressed the progression (HR, 0.17; 95% CI, 0.06-0.46). The IVI-related mortality rate was 2.2%. To reduce the risk of LRTI development after IVI, early NAI therapy should be considered in allo-HSCT recipients, especially with older patients and those with chronic graft-versus-host disease. [Display omitted]