CD4 and infection: The analyses of multiple NK, CD8+ T, CD4+ T and B cell subsets, the production of virus‐specific antibodies, the expression of associated‐activation and exhaustion molecules, the secretion of inflammatory cytokines in patients with moderate COVID‐19 during convalescent period, and the identification of the differences in the cell subsets between SARS‐CoV‐2 and other pathogenic microorganism (non‐SARS‐CoV‐2) infection would provide useful information on immune response against SARS‐CoV‐2.