BRIEF COMMUNICATION High level of Anti SARS-Co-V2 RBD Antibody one year post booster vaccine hospital workers in Indonesia; Was second booster needed?

Healthcare workers in Indonesia acquired a complete 2 doses of Sinovac in early 2021 and first booster dose of Moderna in July 2021. In August 2022, the ministry of health prioritized healthcare workers to acquire the second booster dose of Moderna as antibody levels from the year before may have waned. We conducted a sequential serosurvey aimed to determine the level of SARS CoV2 S-RBD antibody reached by the first vaccine, after the first booster, and before the second booster to understand the dynamics of the antibody level. COVID-19 antibody test was conducted using the FastBioRBDtm test with a maximum limit detection level of 4000 BAU/mL. First serosurvey which was conducted in June 2021, one to six months after Sinovac vaccination, showed a median antibody level of 41.4 BAU/mL (IQR 10 - 629.4 BAU/mL). The second serosurvey was conducted one month (August 2021) after the first Moderna booster vaccine, and showed a median level of 4000 BAU/mL (IQR 3081 - 4000 BAU/mL). While the last serosurvey conducted a year (August 2022) after the booster, showed 4000 BAU/mL (IQR 4000 - 4000 BAU/mL). Only 39 (11.9%) healthcare workers have antibody levels below the maximum level of 4000 BAU./mL We did not see the waning of antibody levels among healthcare workers approximately 1 year after the booster. It increases perhaps due to the natural infection caused by the omicron variant outbreak in early 2022. Based on this fact, we suggest considering if the second booster dose is really necessary. The limited vaccine supply can better be given to the person or other high-risk groups of patients who has a low level of antibody based on serological testing.