A one-year follow-up study on dynamic changes of leukocyte subsets and virus-specific antibodies of patients with COVID-19 in Sichuan, China

Background: SARS-CoV-2 infection causes immune response and produces protective antibodies, and these changes may persist after patients discharged from hospital. Methods: This study conducted a one-year follow-up study on patients with COVID-19 to observe the dynamic changes of circulating leukocyte subsets and virus-specific antibodies. Results: A total of 66 patients with COVID-19 and 213 healthy patients with inactivated SARS-CoV-2 vaccination were included. The virus-specific total antibody, IgG and IgM antibody of patients after one year of recovery were higher than those of healthy vaccinated participants (94.13 vs 4.65, 2.67 vs 0.44, 0.09 vs 0.06, respectively) (P < 0.001). Neutrophil count (OR = 1.73, 95% CI: 1.10-2.70, P = 0.016) and neutrophil-to-lymphocyte ratio (OR = 1.59, 95% CI: 1.05-2.41, P = 0.030) at discharge were the influencing factors for the positivity of virus-specific IgG antibody in patients after one year of recovery. The counts of CD4+ and CD8+ T, B and NK cells increased with the time of recovery, and remained basically stable from 9 to 12 months after discharge. After 12 months, the positivity of IgG antibody was 85.3% and IgM was 11.8%, while the virus-specific antibody changed dynamically in patients within one year after discharge. Conclusions: The SARS-CoV-2 specific antibody of recovered patients showed dynamic fluctuation after discharge, while the leukocyte subsets gradually increased and basically stabilized after 9 months.