Humoral immunity after second dose of BNT162b2 vaccine in Japanese communities: an observational cross-sectional study, Fukushima Vaccination Community Survey

To reveal waning humoral immunity after second dose BNT162b2 vaccinations in a rural Japanese community and determine factors affecting antibody titers. We aimed to report Immunoglobulin G (IgG) antibody against the SARS-CoV-2 spike (S1) protein levels and neutralizing activity in a large scale community based cohort. Methods: Participants in the observational cross-sectional study received a second dose of vaccination with BNT162b2 (Pfizer/BioNTech) and were not previously infected with COVID-19. Questionnaire-collected data on sex, age, adverse vaccine reactions, and medical history was obtained. Results: Data from 2496 participants revealed that older age groups reached a low antibody titer 90–120 days after the second vaccination. Neutralizing activity decreased with age; 35 (13.3%) of those aged ≥ 80 years had neutralizing activity under the cut-off value. Neutralizing activity > 179 days from the second vaccination was 11.6% compared to that at