Vδ2Vγ9T cell clusters 20 and 25 from CR2 panel were expanded in severe and critical COVID-19 (Bonferroni-adjusted P-value range 0.00564–6.39 × 10−8) and characterized by CCR9, CXCR3 and TIGIT expression (Fig. 5d and Supplementary Fig. 14). Here, CCR9 is linked to COVID-19.