Pre-vaccination, the median frequencies of (pooled) vaccine influenza strain-specific CD4+ T cells (per 106 CD4+ T cells) were 1300 and 1200 in the TIV/AS03(≥65) and TIV(≥65) groups; whereas the median frequency was 2000 in the TIV(18–40) group. Here, CD4 is linked to influenza.