Antibody Responses after Bnt162b2 Vaccination in Japanese Geriatric Intermediate Care Facilities

Background: To evaluate antibody responses against the primary series of vaccination of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines in the staff and residents of Japanese geriatric intermediate care facilities.Methods: All subjects (159 staff and 96 residents) received two doses of the BNT162b2 mRNA vaccine 3 weeks apart. Baseline data of subject were collected using a structured form. Serum samples were collected three times: before vaccination, 3 weeks after the first dose, and 4 weeks after the second dose, and anti-receptor binding domain of the spike protein of SARS-CoV-2 [anti-RBD] IgG was measured using two immunoassays.Results: After the second dose, geometric mean titers (GMT) of anti-RBD with both the Abbott and Roche assay were significantly lower in residents than staff (2282 AU/mL vs. 8505 AU/mL, and 258 U/mL vs. 948 U/mL, respectively). Multivariate analysis of characteristics affecting antibody responses (≥1280 AU/mL for Abbott and >210 U/mL for Roche) showed lower odds ratios (ORs) for older age (adjusted OR per 10 year increase [aOR]=0.62, 95% confidence interval (95%CI); 0.38-1.02), steroid usage (aOR=0.09, 95%CI; 0.01-0.60) and regular NSAID usage (aOR=0.16, 95%CI; 0.03-0.88).Conclusions: Elderly people and steroid and NSAID users had lower antibody responses following the second vaccine dose.