IL2 and COVID-19: We found that NAbs correlated well with IFN-γ-secreting and IL-2-secreting T-cell responses after receiving the inactivated vaccine in COVID-19 convalescents (P < 0.01 and P < 0.01) (Fig. 4A and 4B), which indicated a positive correlation between cellular immune and humoral immune response in vaccinated COVID-19 convalescent patients.