Objectives was to measure the level and to identify the structure of SARS-CоV-2 seroprevalence among residents of Podolsk district in Moscow Region during the COVID-19 epidemic period.
Methods. The study was conducted between February and July 2022. Study participants were 312 volunteers from Podolsk city Moscow Region aged 6 – 80 years. A total of 312 volunteers were ranged in to five groups depending on a COVID-status (CoV-ST): group 1 – non-vaccinated-recovered, nV-Recover, 106 people; group 2 – vaccinated-non-contact, V-nC, 32 people; group 3 – recovered-then vaccinated (hybrid), R-V (hybrid), 104 people; group 4 – vaccinated-then contacted-recovered, V-R, 68 people; group 5 – non-vaccinated-non-contact, V-nC, 2 people. The amount of antibodies to SARS-CoV-2 was measured with an quantitative enzyme-linked immunosorbent assay (ELISA) kit for human blood serum tests for detecting a specific immunoglobulin G (IgG) antibodies to RBD S-protein SARS-CoV-2 (anti-IgG RBD S-protein SARS-CoV-2) with resulting a BAU “binding antibody units”. The statistical processed an GraphPad Prism software (version 8.0.1) and Excel statistical package Microsoft? Excel? for Microsoft 365 MSO (verse 2201 16.0.14827.20158). The Pearson’s rank correlation coefficient of parametric measure, descriptive statistics, Wilcoxon test for non-parametric statistics have been performed.
Results. While two (2/312 = 1 %) serum samples from volunteers of group 5 were negative in anti-IgG to RBD S-protein SARS-CoV-2, the three hundred ten (310/312 = 99 %) serum samples from volunteers of group 1 – 4 were positive demonstrating the level of anti-IgG to RBD S-protein SARS-CoV-2 from 19.3 to 42.510 BAU/ml (in average 3.827 BAU/ml, median 1.990 BAU/ml, р < 0.0001). The proportion of total structure of seroprevalence which presented by 89.7 % (278/310 = 89.7 %), 65.8 % (204/310 = 65.8 %) and 55.5 % (172/310 = 55.5 %) cases respectively was introduced by ill-induced, vaccine-induced, and mixed seroprevalences from groups 1, 3 and 4; 2, 3 and 4; 3 and 4 respectively. Blood serum from 87 (87/104 = 28.1 %) seropositive volunteers of group 3 presented by level of IgG antibodies to RBD S-protein SARS-CoV-2 ranged from 500 to 42.510 BAU/ml as well as a direct-moderate correlation between COVID-19-confirmation and volunteer’s history was noted (r = 0.4, р < 0.0001).
Conclusion. A high, a highest and hyperimmune response to SARS-CoV-2 which was prevailed in volunteers with CoV-ST R-V (hybrid) and was detected from 500 to > 26.000 BAU/ml reaching a maximum of 42.510 BAU/ml. These data can reflect a high level of seroconversion among a particular district of Moscow region. In groups 1 – 4 were not diagnostic significance between factors such as gender, age, severity of disease, fact and vaccination shots, vaccine manufacturing technology, time elapsed since disease and level of protective antibodies due to poorly direct or inverse correlation (r = – 0.3, p < 0.0001; r = – 0.2, p < 0.0001; r = 0.3, p < 0.0001).
