GZMB and influenza: To further evaluate cellular effector functions and vaccine-induced cross-reactivity, PBMC samples from the UNISEC study [5,6] were assessed for in vitro responses to FLU-v antigens and a panel of inactivated heterosubtypic influenza strains by means of using dual ELISpot to enumerate IFN-γ- and granzyme-B-producing cells as markers for cytotoxic cellular responses.