Antibody response to the inactivated SARS-CoV-2 vaccine among healthcare workers, Indonesia

BACKGROUND: As healthcare workers (HCWs) are at high risk for infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), they have priority for receipt of the coronavirus disease 2019 (COVID-19) vaccine. The inactivated SARS-CoV-2 vaccine has been used in Indonesia to induce an antibody response against SARS-CoV-2 infection in HCWs. However, information regarding the kinetics of antibodies induced by this vaccine remains scarce. OBJECTIVE: To investigate the magnitude and durability of antibodies against the spike (S) protein (anti-S) in fully-vaccinated HCWs using an electrochemiluminescence immunoassay. RESULTS: Seroconversion of anti-S antibodies was observed among 159 (99.4%) of 160 HCWs without prior SARS-CoV-2 infection 14 days after full-dose vaccination. The level of anti-S antibodies decreased significantly by day 42 post-vaccination compared with day 14 post-vaccination, but persisted for up to 98 days post-vaccination. In contrast, vaccinated HCWs with prior SARS-CoV-2 infection had significantly higher, stable levels of anti-S antibodies compared with vaccinated HCWs without prior SARS-CoV-2 infection. CONCLUSION: The remarkable decline and lower level of anti-S antibodies among HCWs without prior SARS-CoV-2 infection may indicate the need for an additional booster dose of SARS-CoV-2 vaccine for protection against COVID-19. This study of antibody responses induced by the inactivated SARS-CoV-2 vaccine among HCWs may contribute to future policy decisions regarding vaccination.