Evaluation of long-term antibody kinetics in healthcare workers vaccinated with inactivated COVID-19 Vero cell vaccine (CoronaVac), a propensity score-matched observational study

•Long-term immunogenicity of the CoronaVac vaccine was evaluated in healthcare workers (HCWs).•Antibody responses were determined with chemiluminescence immunoassay for binding antibodies and enzyme-linked immunosorbent assay for neutralizing antibodies.•Propensity score analysis was performed to match the subcohort for age.•Antibody titers decreased over time, mainly in HCWs over the age of 40 years.•The results of this study may guide approval decisions for COVID-19 booster vaccines. This study aimed to evaluate the long-term antibody kinetics after vaccinating with an inactivated COVID-19 Vero cell vaccine (CoronaVac) in healthcare workers (HCWs) at a single center in Turkey. For this prospective observational study, Chemiluminescence immunoassay (CLIA) and enzyme-linked immunosorbent assay (ELISA) were used for the determination of binding antibodies (bAb) and neutralizing antibodies (nAb), respectively. Antibody kinetics were compared for the potential influencing factors, and propensity score analysis was performed to match the subcohort for age. Early bAb and nAb response was achieved in all 343 participants. Titers of bAbs against SARS-CoV-2 on 42 days post-vaccination (dpv) were higher in HCWs who were aged