Immunity after the flu shot The seasonal flu shot is currently recommended each year because the influenza viral strains in circulation are continuously changing and because the antibody responses produced by the vaccine decline over time. In a human study of healthy volunteers, Davis et al. tracked antibody responses after flu vaccination. They investigated whether the vaccine led to the generation of antibody-secreting plasma cells in the bone marrow, a lymphoid organ that supports the survival of these cells for years. Although vaccination did generate influenza-specific cells, most were short-lived and lost within 1 year. The fact that a small number did persist over 1 year raises prospects that the longevity of flu vaccines can be improved and provides key information for the development of universal vaccines against influenza. Science , this issue p. 237