Influenza in patients with hematologic disease: an ounce of prevention is worth a pound of cure

The article by Wei et al. in this issue of Leukemia and Lymphoma describes severe outcomes among 11 hospitalized patients with hematologic disease infected with novel influenza A (H1N1) [1]. These included lower respiratory tract involvement in nine patients, need for mechanical ventilation in three patients, and death in five patients. Severe disease and poor outcome in patients with hematologic conditions infected with novel influenza A (H1N1) has been documented in other recent reports [2,3]. These findings parallel the experience with seasonal influenza in this population, with high proportions of poor outcomes including lower respiratory tract involvement [4,5] and mortality [6,7]. Outcomes may remain poor despite appropriate treatment with antivirals, as is described in the article by Wei et al. Given the potentially grave consequences of influenza infection in this population, it is paramount to prevent it. There are currently three main strategies to prevent influenza infection: infection control measures including isolation of symptomatic patients and prevention of disease transmission from their contacts; vaccination of patients and their close contacts; and use of antivirals for prophylaxis (Table I). Among the 11 patients described by Wei et al., seven acquired the infection while hospitalized [1]. These cases might have been prevented by strict adherence to infection control measures. In a recent Cochrane review, the main intervention shown to be effective in prevention of transmission of respiratory viruses was frequent hand-washing [8]. This intervention appears to be particularly efficacious when applied to children in the same household as the patient. In the same review, use of barriers, including masks, gloves, and gowns, in inpatient settings was also found to be effective [8]. Special care should be taken to prevent transmission of influenza from healthcare professionals to patients; hospital employees should be vaccinated against the circulating influenza strains, and any healthcare worker experiencing respiratory symptoms should not be allowed to come to work. When a patient with a hematologic condition is hospitalized with influenza, isolation precautions should be strictly maintained until symptoms resolve and repeat virologic studies are negative; it is well documented that viral shedding in this population can be prolonged, even in the absence of symptoms [9]. The second strategy is vaccination. The main concern in vaccinating this population against influenza is whether they are able to mount an adequate immune response to the vaccine. Several studies have documented low rates of humoral response to the influenza vaccine in this population, with a response rate as low as 19% in patients with multiple myeloma. However, the response rate is highly variable and depends on the underlying malignancy, chemotherapy used, and the assay used to assess immunologic response [10]. Patients within 6 months of hematopoietic stem cell transplant (HSCT) have poor rates of response to influenza vaccination [11], as do patients within 1 week of receiving standard chemotherapy [12]. Although response rates may be low, inactivated influenza vaccine should be recommended for all patients with hematologic conditions. In recipients of HSCT and