 The investigators plan to study the immunogenicity of two different types of the influenza vaccine in 240 allogeneic stem cell transplant patients during the 2015-2016 season. Patients will be randomized to receive either adjuvanted influenza vaccine or nonadjuvanted. Antibody titers will be evaluated by a standard hemagglutination inhibition assay. The investigators hypothesize that the patients who receive the adjuvanted influenza vaccine will reach significantly higher response to the vaccine. This study advances research on the prevention of serious viral infections in transplant recipients. 