CD4 and COVID-19: CD4+ T cell responses to the spike MP correlated with both RBD IgG titers (r = 0.6; P = 0.007) and spike IgG titers (r = 0.75; P = 0.0003) in participants with convalescent COVID-19 (Figure 2, F and G) but not MIS-C (Figure 2, C and D).