Anti-spike protein antibody responses to BNT162b2 mRNA vaccine: A single-center survey in a COVID-19 non-epidemic area in Japan

Background: There are a few reports on antibody responses after a two-dose BNT162b2 vaccination in non-epidemic areas. We evaluated this phenomenon. Methods: A total of 344 healthcare workers were vaccinated, and the serum anti-receptor-binding domain (RBD) antibody concentrations before and after two weeks following the two-dose BNT162b2 vaccination were measured using electro chemiluminescence immunoassay system. Results: Before vaccination, the antibody titers of all participants were less than 0.6 U/mL. After two doses of the BNT162b2 vaccine injection in 342 participants (2 excluded), a high seroconversion rate (99.7%) was observed. The average (±standard deviation) serum anti-RBD antibody titers were 2324 ± 1739 U/mL. Antibody levels in females and males were 2443 ± 1833 U/mL and 1908 ± 1287 U/mL, respectively (p = 0.037). Conclusion: In a non-epidemic area, two BNT162b2 doses induced a satisfactory antibody response, and the antibody concentrations in females were higher than in males.