Community acquired influenza requiring hospitalization: vaccine status is unrelated to morbidity in children with cancer.

BACKGROUND: Community acquired influenza can be severe and there are few data regarding hospitalization for children with cancer and influenza. Association between prior vaccination and infection severity has not been studied, although vaccination is standard practice. PROCEDURE: Patients with malignancy or prior stem cell transplant (SCT) were identified using a database of children with laboratory confirmed influenza (2000-2005). Other data collected included receipt of vaccine, absolute neutrophil count (ANC) and absolute lymphocyte count (ALC). These were compared with intensive care unit (ICU) stay, respiratory complications and hospital days. RESULTS: There were 39 patients with laboratory-confirmed influenza with a median age of 6.9 years. Twenty-four (62%) were on cancer therapy at time of infection and 18 (46%) had received the influenza vaccination that season. Measures of immune status included ANC at time of infection (median 1,530 cells/microl; inter-quartile range, 315, 4347), presence of graft versus host disease 2 (5%) and steroid therapy 4 (10%) patients. All had a low ALC (median 448 cells/microl; IQR 189, 861). Respiratory complications occurred in 8 (20%), ICU admissions in 4 (10%) and death in 2 (5%) patients. Median hospital stay was 2 days. All ICU admissions occurred in unvaccinated patients (P = 0.1). Vaccine status, ANC (<1,000 cells/microl vs. >1,000) and ALC (<500 cells/microl vs. >500) were not associated with length of stay or respiratory complications. CONCLUSIONS: Influenza infection can be severe in children with cancer and complications occur despite vaccination. Prospective evaluation of vaccine response is worthy of future study.