ABSTRACT
Background: Healthcare workers (HCWs) get priority access to the coronavirus disease 2019 (COVID-19) vaccination since they are at high risk of infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). In Indonesia, an inactivated SARS-CoV-2 vaccination was utilized to generate an antibody response against SARS-CoV-2 infection in healthcare workers. However, data on the kinetics of antibodies generated by this vaccination remains inconsistent. This study aimed to assess quantitative antibody titers on the 28th and 90th days after the second dose of COVID-19 immunization. Methods: This prospective cohort study involved 189 HCWs. The samples were analyzed by Roche® Elecsys Anti-SARS-CoV-2 serology test for quantitative SARS-CoV-2 total antibody. Data were analyzed using STATA version 17 for Windows. Results: Most of the subjects (75.1%) were females, with a male-to-female ratio of 1:3. Most subjects are medic (68.8%), do not have comorbid (75.8%), have not been infected with Covid-19 (73.5%), and not a close contact (55%). Previous COVID-19 infection affects antibody titers significantly (p<0.0001). Moreover, quantitative antibody titers differ significantly between 28-and 90-days following the second dose of Sinovac vaccination (p<0.0001). However, age, gender, profession, comorbidity, and history of close contact did not significantly associate with antibody titers (p=0.150, p=0.105, p=0.367, p=0.063, and p=0.696, respectively). Conclusions: Our study shows that antibody titers on 90-days following the second dose of COVID-19 vaccination are significantly lower than after 28 days. Moreover, antibody titers on survivors are higher than on those who have not been infected. Further multi-institutional study with a larger sample and longer follow-up is necessary to clarify and confirm our findings. © 2023, Sanglah General Hospital. All rights reserved.