Researchers from Nationwide Children’s Hospital, Baylor Institute for Immunology Research, and Mount Sinai School of Medicine have found an important mechanism by which seasonal flu vaccines can stimulate the body’s immune responses. The researchers analyzed blood samples taken before and after influenza vaccination from three groups of healthy study participants: two sets of adults and a group of children who received the flu vaccine during the 2010-2011 season. The blood analysis found that a temporary increase in a subset of helper T cells can help B cells produce influenza-specific antibodies, adding to the immune response. The T cells positively correlated with increased antibodies against each flu virus strain examined, except against the swine-origin H1N1 virus in the children’s group. The findings are published in Science Translational Medicine.