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Recent studies have demonstrated a marked decrease in peripheral lymphocyte levels in patients with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Few studies have focused on the changes of NK, T- and B-cell subsets, inflammatory cytokines and virus-specific antibodies in patients with moderate COVID-19. A total of 11 RT-PCR-confirmed convalescent patients with COVID-19 and 11 patients with non-SARS-CoV-2 pneumonia (control patients) were enrolled in this study. NK, CD8 + T, CD4 + T, Tfh-like and B-cell subsets were analysed using flow cytometry. Cytokines and SARS-CoV-2-specific antibodies were analysed using an electrochemiluminescence immunoassay. NK cell counts were significantly higher in patients with COVID-19 than in control patients (P = 0.017). Effector memory CD8 + T-cell counts significantly increased in patients with COVID-19 during a convalescent period of 1 week (P = 0.041). TIM-3 + Tfh-like cell and CD226 + Tfh-like cell counts significantly increased (P = 0.027) and decreased (P = 0.022), respectively, during the same period. Moreover, ICOS + Tfh-like cell counts tended to decrease (P = 0.074). No abnormal increase in cytokine levels was observed. The high expression of NK cells is important in innate immune response against SARS-CoV-2. The increase in effector memory CD8 + T-cell counts, the up-regulation of inhibitory molecules and the down-regulation of active molecules on CD4 + T cells and Tfh-like cells in patients with COVID-19 would benefit the maintenance of balanced cellular and humoural immune responses, may prevent the development of severe cases and contribute to the recovery of patients with COVID-19., (© 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)