CD8A and COVID-19: After vaccination against COVID-19, T-cell immunity (such as the Th1 cell response), B-cell immunity (such as the germinal center response), and other immune responses may be produced.19,21 Differentiated Th cells can enhance the immune response in the body by promoting the activation of CD8+ T cells and secreting IFN-γ.31 With the aid of Th cells, activated B cells proliferate and divide in lymphatic follicles to form germinal centers, eventually form plasma cells, and memory B cells secret high-affinity antibodies.