Association of total and neutralizing SARS-CoV-2 spike -receptor binding domain antibodies with epidemiological and clinical characteristics after immunization with the 1st and 2nd doses of the BNT162b2 vaccine

Abstract

\n Background\n Data regarding the association of antibody levels elicited after immunization with the BNT162b2 mRNA Covid-19 vaccine with epidemiological and clinical parameters are limited.\n \n Methods\n We prospectively measured the total (TAbs-RBD) and the neutralizing antibodies (NAbs-RBD) against the receptor binding domain (RBD) of SARS-CoV-2 spike protein in a cohort of 268 Healthcare workers before immunization, 20 days after the 1st dose and 30 days after the 2nd dose of the BNT162b2 vaccine. A statistical analysis for possible association of antibodies’ levels with epidemiological and clinical parameters was performed.\n \n Results\n The mean age (±SD) of the participants was 45.45 years (± 11.93) (range: 24-70 years) and 211 (79.9%) were females. Statistically significant differences were detected regarding both TAbs-RBD and NAbs-RBD between the first and second doses of the vaccine (P<0.001). The median (IQR) percentage (%) of NAbs-RBD after the 1st dose was 51.07% (31.60%) and after the 2nd dose 95.31% (3.70%) (P<0.001).The correlation between the TAbs-RBD and NAbs-RBD was after the 1st dose, Spearman’s, rho: 0.861 (P<0.001) and after the 2nd dose rho: 0.989 (P<0.001). Twenty days after the 1st dose, 56/264 (21.2%) of the participants did not have detectable NAbs-RBD, while one month after the 2nd dose all of them had detectable NAbs-RBD. After the 2nd vaccine dose, a statistically significant negative association of TAbs-RBD was detected for age (P<0.001), smoking (P=0.011), and immunosuppressive medications (P<0.001), while a positive association was detected for BMI (P=0.004) and systemic adverse events after immunization (P=0.001).\n \n Conclusion\n A significant correlation of TAbs-RBD and NAbs-RBD was detected after both vaccine doses. Older age, smoking, and immunosuppressive medications negatively affected the final antibody level after SARS-CoV-2 immunization. Our findings emphasize the significance of the 2nd vaccine dose especially in the older age groups.\n