 Immune responses were measured by detection of influenza-specific antibodies as measured by the standard hemagglutination inhibition HAI assay. Influenza-specific serum antibody isotype levels were determined and nasal swab specimens were analyzed for the expression of influenza-specific immunoglobulin A IgA. Serum was analyzed for its ability to neutralize viral particles from infecting Madin-Darby canine kidney cells microneutralization. Baseline immunosuppression as measured by expression of T- and B-lymphocyte subsets was compared to immunosuppression at time points after vaccination. The duration of viral replication and the titers of live-attenuated influenza virus shed was evaluated from nasal swab specimens collected at scheduled time points after administration of FluMist. 