 Influenza virus is an important cause of morbidity in the lung transplant population and can lead to viral and bacterial pneumonia and contribute to the bronchiolitis obliterans syndrome. Although the annual influenza vaccine is recommended for lung transplant patients, studies have shown that a single intramuscular i.m. dose has poor immunogenicity. There are no studies that define the effect of intradermal doses in this population. We plan to study the immunogenicity of a two-dose regimen of influenza vaccine in 50 lung transplant patients during the 2006-2007 season. After the initial i.m. injection, a second dose will be given intradermally 4 weeks later. Antibody titers will be evaluated by a standard hemagglutination inhibition assay. We hypothesize that the second dose intradermally will significantly increase the proportion of vaccine responders. 