The frequencies of naïve (CD45RA+) and non-naïve (CD45RA–) CD4+ T cells as well as the frequencies of CD45RA−CXCR5– Th and CD45RA−CXCR5+ PD-1+ Tfh-like cells within CD4+ T cells were not significantly different in COVID-19 patients vs controls (Figs 7A and S9A). Here, CD4 is linked to COVID-19.