CD4 and infection: CD4+ T cell analysis revealed a higher median number of CD4+CD45RO+ memory T cells three months post-infection in the hospitalised subgroup, compared to non-hospitalised individuals, and a higher median number of CD4+CD45RO+IL-2+ memory T cells was also observed upon Omicron peptide pool stimulation in vitro in the hospitalised subgroup (Figures 3A, B).