The dynamics of quantitative SARS-CoV-2 antispike IgG response to BNT162b2 vaccination.

Vaccination for SARS-CoV-2 is necessary to overcome coronavirus disease 2019 (COVID-19). However, the time-dependent vaccine-induced immune response is not well understood. This study aimed to investigate the dynamics of SARS-CoV-2 antispike immunoglobulin G (IgG) response. Medical staff participants who received two sequential doses of the BNT162b2 vaccination on days 0 and 21 were recruited prospectively from the Musashino Red Cross Hospital between March and May 2021. The quantitative antispike receptor-binding domain (RBD) IgG antibody responses were measured using the Abbott SARS-CoV-2 IgGII Quant assay (cut off ≥50 AU/ml). A total of 59 participants without past COVID-19 history were continuously tracked with serum samples. The median age was 41 (22-75) years, and 14 participants were male (23.7%). The median antispike RBD IgG and seropositivity rates were 0 (0-31.1) AU/ml, 0.3 (0-39.5) AU/ml, 529.1 (48.3-8711.4) AU/ml, 18,836.9 (742.2-57,260.4) AU/ml, and 0%, 0%, 98.3%, and 100% on days 0, 3, 14, and 28 after the first vaccination, respectively. The antispike RBD IgG levels were significantly increased after day 14 from vaccination (p < 0.001) The BNT162b2 vaccination led almost all participants to obtain serum antispike RBD IgG 14 days after the first dose.