Assessment of T cells by MHC multimers and scRNAseq to profile antigen specific T cells from multiple SARS-CoV-2 proteins after repeated exposure to antigens, including vaccination, previous infection, and breakthrough infection, found no evidence of narrowing of the T cell repertoire from repeated exposure.93 Repeated exposure, including those with omicron breakthrough infection after spike based vaccination, produced a broad CD8+ T cell response that might better prepare individuals against future new variants. This evidence concerns the gene HLA-C and infection.