Vaccination induces the development of long-lasting immunity necessary for a sustained and essential protective antibody response. Understanding how long the humoral immune response induced by the severe acute respiratory syndrome coronavirus-2 (SaRS-CoV-2) inactivated vaccine lasts is important to create an effective immunization scheme. This study aimed to detect the first, third, sixth month con- centrations and seroconversion rates of the antibodies induced by the inactivated vaccine. The study included 282 healthcare workers who were vaccinated at days 0 and 28 by the inactivated SaRS-CoV-2 vaccine (3 μg/0.5ml). anti-S-RbD-IgG (receptor binding domain) antibody concentrations and serocon- version rates were examined in vaccinated healthcare workers at the first, third and sixth months after the vaccination. MaGLUMI SaRS-CoV-2 S-RbD IgG (CLIa) (Snibe Diagnostics, Chinese) kit was used for the detection of antibodies. The mean age of the healthcare workers was 38.93 ± 10.59 (min= 21-max= 64). after the administration of the second vaccine dose, the participants were found to be reactive for anti-S- RbD-IgG antibodies by 98.2% and 97.8% at the first and third months, respectively,. The decrease in the mean plasma concentrations of anti-S-RbD IgG was observed as 56.7% in the cohort with only two doses of the vaccine (first month: 42.4 aU/ml versus third month: 18.2 aU/ml). In the cohort with a history of coronavirus disease 2019 (COVID-19) prior to the vaccination, the decrease was observed as 25.1% (first month: 58.29 versus third month: 43.64 aU/ml) and at a mean of 57.4 (0-90) days prior to vaccination, the decrease rate was 43.1% (first month: 55.05 aU/ml versus third month: 31.28 aU/ml), keeping more stable in participants infected at a mean of 183.1 (91-330) days prior to vaccination(a decrease of 5.2%; with 62.34 aU/ml at first and 59.08 aU/ml at third months). at the end of the sixth month, antibodies could not be detected in 16.7% of people who (n= 42) received two doses of the inactivated vaccine, and the amount of anti-S-RDb IgG decreased by an average of 52.5% compared to the third month, and by 74.8% compared to the first month. antibody concentrations at the first, third, and sixth months after the vaccination with two doses of the inactivated SaRS-CoV-2 vaccine were found to be decreased and at the sixth month, the rate of non-reactive people was 16.7%. as participants who had COVID-19 at a mean of 181 (90-330) days before the vaccination presented with a more stable antibody level, it can be concluded that a booster at months 6-12, resulting in a schedule of 0-1-6 months, is recommended for the inactive SaRS-CoV-2 vaccination for effective herd immunity.