Outcomes of Influenza Infections in Hematopoietic Cell Transplant Recipients: Application of an Immunodeficiency Scoring Index.

Hematopoietic cell transplant (HCT) recipients have lower immune response to influenza vaccination and are susceptible to lower respiratory tract infection (LRI) and death. We determined clinical characteristics and outcomes of laboratory-confirmed influenza, including 2014/H3N2 infection, in 146 HCT recipients. An immunodeficiency scoring index (ISI) was applied to identify patients at high risk for LRI and death. Thirty-three patients (23%) developed LRI and 7 (5%) died within 30 days of diagnosis. Most patients received antiviral therapy (83%); however, only 18% received it within 48 hours of symptom onset. The incidence of LRI was significantly higher in the ISI high-risk group than it was in the low-risk group (P < .001). Receiving early antiviral therapy was associated with a substantial reduction in LRI for all ISI risk groups with the greatest risk reduction observed in the high-risk group. When compared with previous seasons, no significant differences in patient outcomes were observed during the 2014/H3N2 season; however, antiviral therapy was more promptly initiated in the latter season. The ISI that was originally developed for respiratory syncytial virus may help identify HCT recipients at risk for progression to LRI and mortality after influenza infection. These patients should be monitored more closely. Early initiation of antiviral therapy for influenza in HCT recipients, regardless of the ISI risk group, may improve morbidity as well as mortality.