CD8A and infection: Of interest, while the percentage of spike-specific T cells induced by 3 vaccine doses was similar between participants who experienced breakthrough infection (n=36) compared to those who remained COVID-19 naive (n=54) when analyzed altogether (P=0.47 for CD4, P=0.28 for CD8), we found that OA who subsequently became infected (n=8) displayed lower vaccine-induced T-cell responses compared to OA who remained uninfected (n=32) (P=0.03 for CD4, P=0.003 for CD8) (Supplementary Figure 4).