Gardulf A, et al. - Researchers intended to identify predictive markers for those who developed a humoral immune response after influenza vaccination. Responders were those who had a 4-fold titer increase of the hemagglutinin inhibition test (≥ 1:40) and these were compared to non-responders for clinical, immunological and genetic markers. Enteropathies were detected in a significantly higher proportion of the responders who exhibited a Euroclass SmB^-Tr^norm21^norm profile with a post-germinal center B cell pattern in blood, relative to non-responders. In non-responders, common variable immunodeficiencies (CVID) related human leukocyte antigen (HLA) markers were not identified. Overall, protective antibody levels post-A(H1N1) vaccination were detected in nearly one-fifth of the CVID patients. Selected clinical and immunological markers possibly predictive of a positive outcome of influenza vaccination were also identified.