Epidemiology and clinical characteristics of pandemic (H1N1) 2009 influenza infection in pediatric hemato‐oncology and hematopoietic stem cell transplantation patients

Background For children with hemato‐oncologic diseases, especially after hematopoietic stem cell transplantation ( HSCT ), the risk for developing complications related to pandemic influenza A (H1N1) 2009 (pH1N1) infection is largely unknown. Methods A retrospective chart study was performed of pH1N1 cases diagnosed between O ctober 2009 to J anuary 2010 in the hemato‐oncologic unit of the U niversity C hildren's H ospital of D üsseldorf, G ermany. Findings In total, 21 children were diagnosed with laboratory‐confirmed pH1N1; in 16 patients with malignancies (acute leukemia 7, lymphoma 4, solid tumors 2, others 3) and in 5 with benign hematologic disorders. Five patients had undergone prior HSCT , although 1 patient was diagnosed during conditioning therapy with high‐dose chemotherapy in preparation for haploidentical HSCT . Most frequent symptoms were fever (>38.5°C) and cough (in 100%), and rhinorrhea (57%). The 2 patients acquiring pH1N1 infection under high‐dose or intensive chemotherapy did not require intensive care or mechanical ventilation, and both recovered under antiviral therapy. Oseltamivir was administered to 11 patients; in 1 patient, therapy was switched, on a compassionate‐use basis, to intravenous zanamivir because of lack of clinical improvement after oseltamivir therapy. Complications were hospitalization (19%), demand of oxygen supplementation, delay/interruption of antineoplastic therapy, and prolonged administration of antibiotics and antipyretics. Conclusion In the investigated patient population, pH1N1 was mild in most cases, but was associated with substantial morbidity in a proportion of patients and led to interruption and delay in anticancer treatment.