The immunity status after the sever acute respiratory syndrome coronavirus-2 (SARS-CoV-2) can determine the protection against reinfection and efficacy of vaccination. Although the mechanisms of SARS-CoV-2 induced immune response need further investigation to provide more data on innate and adaptive immune responses. It can be expected that in case of fail of SARS-CoV-2 induced humoral immunity the adaptive one is developed. The NovaLisa SARS-CoV-2 (COVID-19) IgG ELISA diagnostical kit (NovaTec Immunodiagnostica GmbH, Germany) for in vitro diagnostic and Human Ki67 ELISA kit (MyBioSource Inc, USA) were used. The study has been performed according to the ELISA kits specific protocols; the absorbance was measured at 450 nm wavelength. For the calculation of results we used the manufacturers’ guidelines.
It has been revealed that: a) 16 (32.7%) samples are negative; b) 5 (10.2%) samples are equivocal; and c) 28 (57.1%) samples are positive for IgG for nucleocapsid protein of SARS-CoV-2. Median levels of Ki67 in: a) negative for IgG of SARS-CoV-2 nucleocapsid protein samples is 14.95 ng/ml; b) equivocal samples is 10.6 ng/ml; and c) positive - 8.3 ng/ml. Increased level of Ki67 correlates with the negative status for IgG of SARS-CoV-2 nucleocapsid protein.