In COVID-19–naive donors, WT S–specific CD4+ T cells expressing AIM (CD69+CD137+) were detected after the first and second vaccination (Fig. 4B, T3 to Vx13, P = 0.0374; T3 to Vx23, P = 0.0016, Kruskal-Wallis test). Here, TNFRSF9 is linked to COVID-19.