Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, United States.; Futian District Center for Disease Control and Prevention, Shenzhen, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Laboratory Animal Center, Sun Yat-sen University, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.; Department of Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.; National Medical Products Administration (NMPA) Key Laboratory for Quality Monitoring and Evaluation of Vaccines and Biological Products, Guangzhou, China.

Recent exposure to seasonal coronaviruses (sCoVs) may stimulate cross-reactive antibody responses against severe acute respiratory syndrome CoV 2 (SARS-CoV-2). However, previous studies have produced divergent results regarding protective or damaging immunity induced by prior sCoV exposure. It remains unknown whether pre-existing humoral immunity plays a role in vaccine-induced neutralization and antibody responses. In this study, we collected 36 paired sera samples from 36 healthy volunteers before and after immunization with inactivated whole-virion SARS-CoV-2 vaccines for COVID-19, and analyzed the distribution and intensity of pre-existing antibody responses at the epitope level pre-vaccination as well as the relationship between pre-existing sCoV immunity and vaccine-induced neutralization. We observed large amounts of pre-existing cross-reactive antibodies in the conserved regions among sCoVs, especially the S2 subunit. Excep t for a few peptides, the IgG and IgM fluorescence