Serological reactivity of inactivated SARS-CoV-2 vaccine based on an S-RBD neutralizing antibody assay

Abstract

Objectives: This study aimed to explore the regularity of S-RBD domain antibody reactivity after immunization with inactivated SARS-CoV-2 vaccine and evaluate the effect of this vaccine on the immune response. Design or methods: Venous blood samples were collected from 1156 healthcare workers who participated in the phase III clinical trial of the SARS-CoV-2 inactivated vaccine. The S-RBD domain antibody levels in the serum were detected by ELISA 14 days after the first and second active immunization, respectively. Results: The positive rates after inoculation of the first and second vaccination of S-RBD domain antibody against SARS-CoV-2 were 28.03% and 86.76%, respectively. The mean inhibition rate of S-RBD domain antibody against positive samples was 57.18 ± 18.87% after the second vaccination at 14 days. Sex and age had no effects on the positive rate. The positive rate was decreased in the high BMI group. Single-factor logistic analysis showed that there was no significant correlation between age and positive rate. BMI was negatively correlated with the positive rate. Conclusions: After 2 immunizations, the positive rate of SARS-CoV-2 S-RBD domain antibody was high, and the vaccine had good immunogenicity. The improvement of the immune strategy should focus on the effects of BMI and other factors.

Keywords

• COVID-19
• Inactivated SARS-CoV-2 vaccine
• S-RBD domain antibody
• Immunogenicity
• BMI