Thus far, post‐vaccination changes in numbers of circulating follicular (CXCR5+) CD4+ T cells and plasmablasts (CD19 + CD27 + CD38+) at day 7 were described as some of the best correlates of antibody responses to influenza vaccination (Koutsakos et al., 2019; Ueno, 2019). The gene discussed is CD19; the disease is influenza.