CD4 and infection: We found that, within the infection-experienced cohort, preexisting levels of spike-specific CD4 memory T cells and spike-specific memory B cells were significantly correlated to the fold change of several proinflammatory cytokines, notably the IFN-inducible cytokines CXCL10 and CXCL11, at 24 hours after the first vaccine dose (Figure 8).