SARS-CoV-2 Antibody Response and Sustainability after a Third Dose of BNT162b2 in Healthcare Workers at Health Promotion Centers

Abstract

The aim of this study was to determine the antibody response and the sustainability of immunogenicity after a third dose of BNT162b2 (BNT) in homologous [ChAdOx1 (ChAd)/ChAd, BNT/BNT, and mRNA-1273 (Moderna)/Moderna] and heterologous (ChAd/BNT) vaccinations of two primary doses with different schemes. This prospective observational study recruited consenting healthcare workers from 16 health checkup centers in 13 Korean cities. Three-point blood tests were analyzed as the antibody response after the third vaccination: T3-1 (1 month after the third dose), T3-3 (3 months after the third dose), and T3-4–10 (4–10 months after the third dose). SARS-CoV-2 antibodies were measured using a chemiluminescence microparticle immunoassay with SARS-CoV-2 IgG II Quant in the ARCHITECT system (Abbott Diagnostics). The antibody levels were significantly higher in the Moderna /Moderna and BNT/BNT groups than in the ChAd/ ChAd and ChAd/BNT groups (p p < 0.001). The third dose of BNT induced an increased humoral immune response in various vaccination schemes, which was more prominent for the two primary doses of homologous mRNA vaccines. However, this immunogenicity decreased within 3–10 months after the third dose. These results suggest that another booster dose (a fourth dose), which would be able to counteract SARS-CoV-2 variants, is needed.

Keywords

• third dose
• vaccination
• SARS-CoV-2
• anti-spike-protein receptor-binding domain (S-RBD) antibodies
• mRNA vaccines