Previous research has also found exhaustion phenotypes of CD8+ T cells in patients with severe COVID-19, which is caused by the upregulation of inhibitory receptors (IRs), which may impair host defences and lead to poor disease outcomes (Caruso et al., 2020; De Biasi et al., 2020; Diao et al., 2020; Laing et al., 2020; Schultheiß et al., 2020; Song et al., 2020; Zheng et al., 2020). Here, CD8A is linked to COVID-19.