The sensitivity and specificity of SARS-CoV-2 serological tests vary widely. The results of three serological tests: EIA (binding antibodies), VNT (NT antibodies), and FIA (sVNT; sNT antibodies) were compared in three groups of patients: vaccinated individuals (N=62); patients who recovered from COVID-19 (N=62) and vaccinated individuals infected with SARS-CoV-2 after vaccination (N=28). SARS-CoV-2 binding antibodies, NT antibodies, and sNT antibodies were detected in 93.1%, 84.2%, and 85.6% of patients. The highest detection rates were observed in vaccinated + COVID-19 patients (100/96.4/100%), compared to 100/96.7/85.5% in COVID-19 patients. The lowest detection rates were in vaccinated individuals (88.5/69.2/84.6%). In There were significant differences in antibody levels between groups tested using EIA. NT antibody titers did not differ among vaccinated individuals and COVID-19 patients; however, in vaccinated + COVID-19 patients, significant differences were found using different viral strains. The lowest median titer was for the Omicron variant (64) compared to the Alpha variant (256), Delta variant (128), and Wuhan strain (128). Additionally, the sNT antibody levels differed between groups with the highest positivity of inhibition (median) in vaccinated + COVID-19 patients (100%) in comparison with COVID-19 patients (92%) and vaccinated individuals (96%). In vaccinated individuals, there was a significant strong positive correlation between EIA/VNT, EIA/sVNT, and VNT/sVNT. COVID-19 patients showed a moderate positive correlation between all serological tests, while vaccinated + COVID-19 patients showed a significant moderate positive correlation only between EIA and sVNT. The frequency of positive sVNT detection rates depended on the NT titer and was lowest in samples with low NT titers (8 and 16). The presented results showed that sVNT is useful in patients with high antibody levels. Due to the possibility of false-negative results, it cannot entirely replace the traditional VNT.