Antibody response after two doses of homologous or heterologous SARS‐CoV‐2 vaccines in healthcare workers at health promotion centers: A prospective observational study

Assaying of anti‐spike‐protein receptor‐binding domain (S‐RBD) antibodies are used to aid evaluations of the immune statuses of individuals. The aim of this study was to determine the antibody response after two doses of homologous or heterologous severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) vaccines and to identify the factors affecting this response among healthcare workers (HCWs) at health promotion centers. In this prospective observational study, 1095 consenting HCWs were recruited from 16 health checkup centers and were tested at T0 (day of first dose), T1‐1 (1 month after first dose), T2‐0 (day of second dose), T2‐1 (1 month after second dose), and T2‐3 (3 months after second 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). At T1‐1, anti‐SARS‐CoV‐2 S‐RBD IgG levels were significantly higher in participants who received messenger RNA (mRNA) vaccines than in those who received viral vector vaccines (p