The third inactivated vaccine booster dramatically enhanced SARS-CoV-2 antibody responses and did not influence the profile of prothrombotic antibody.

The purpose of this study is to investigate the production of both severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific antibodies and autoantibodies in serum following the third booster vaccination of the inactivated COVID-19 vaccine, and to study the effect of B cell subsets with CD27 and CD38 phenotypes in peripheral blood on antibody production. Routine blood indexes, SARS-CoV-2 antibodies, platelet factor 4 and seven antiphospholipid antibodies were detected both before and 2 months after vaccination in the medical staff of the Zhongnan Hospital of Wuhan University. Peripheral blood B cell subtypes were detected before vaccination. Following immunization, the positive rate of anti-N-S1 immunoglobulin (IgG) had increased from 24.8% to 91.3% and the average antibody concentration had increased by 11 times. The positive rate of neutralizing antibody had increased from 24.8% to 91.3%, the average antibody concentration had increased by 12 times, and the primary increased anti-S1 IgG subtype was that of IgG1. Peripheral blood CD27 + CD38+ B cells were positively correlated with antibody levels after vaccination and were a predictor of the antibody response. In addition, although some indicators showed slight absolute changes, the blood parameters and antiphospholipid antibodies of most volunteers were normal both before and after COVID-19 inactivated vaccine inoculation, and there was no statistical difference in abnormal rates either before or after inoculation. Antibodies in vivo were increased after vaccination with the inactivated vaccine, and IgG1 was the main subtype involved in response to the vaccine. Vaccination with the inactivated COVID-19 vaccine did not appear to affect thrombus-related autoantibodies.