AIM+ CD4+ and CD8+ T cells were sorted via flow cytometry and processed for scRNA-seq from a previously infected donor sampled before and soon after vaccination (n = 1), recently infected convalescent donors sampled on day 35 only (n = 3), and donors with a history of mild (n = 3) or severe (n = 3) COVID-19 sampled at 6–9M and 18M (Fig. 3A, fig. This evidence concerns the gene CD4 and COVID-19.