Waickman et al. (2019) characterized the activated and clonally expanded T cells in response to the vaccine of dengue virus and assessed the T cell immune response following vaccination. Wang et al. (2021) delineated the TCR repertoires of coronavirus disease 2019 (COVID-19) patients and observed distinct T cell clonal expansion and skewed VDJ gene usage in COVID-19. Liao et al. (2020) detected the transcriptome and TCR profile of the bronchoalveolar lavage fluid of patients with COVID-19 and found highly clonally expanded CD8+ T cells in patients with mild COVID-19. Here, CD8A is linked to COVID-19.