Specific Aim 2. To test the hypothesis that antibody titers to influenza vaccine antigens are associated with cardiopulmonary outcomes. In a subset of participants, antibody titers by hemagglutination inhibition assays to influenza vaccine antigens at baseline and at 4 weeks following randomization will be determined, corresponding to achievement of maximal antibody titer levels after vaccination. The association between geometric mean titers post-vaccination and the occurrence of death or cardiopulmonary hospitalization (primary outcome measure of Specific Aim 1) will be assessed.