Our study observed a group of 1063 people, 786 females (74%) and 277 males (26%), in the age bracket between 18 and 89 years old. People over 50 years old constituted 45% (N=479) of the group. Because of different postvaccination reactions, three subjects we considered early hyper responders IgM and IgG, and we excluded them from further evaluation. The final group of 1060 subjects (Table 1.) we divided into five subgroups: Control group G0 (N=154) was unvaccinated persons with no clinical signs of COVID-19 who tested negative for SARS CoV-2 by RT-PCR. Group G1 (N=76) included entirely symptomatic COVID-19 patients who tested positive for SARS CoV-2 by RT-PCR. Group G2 included 472 healthy individuals vaccinated with both doses of Comirnaty. Group G3 included 42 persons vaccinated with AstraZeneca (N=21), Moderna (N=19), and Johnson & Johnson (N=2) according to the vaccination scheme. Group G4 included 312 COVID-19 convalescents vaccinated with Comirnaty. Group G5 consisted of 4 individuals with COVID-19 convalescents infected with SARS CoV-2 after a complete systemic vaccination cycle. Two positive RT-PCR tests confirmed the infection.
After a retrospective analysis of concentrations of SARS CoV-2 IgG antibodies in group G0 (N=154), we identified subgroup G01 of 43 persons who had higher than cut-off value (0.2 AU/ml) concentrations of specific IgG antibodies. The existence of specific SARS CoV-2 antibodies we recognized as evidence of viral contact, and the patients were qualified as SARS CoV-2 convalescents with no symptomatic COVID-19 history. Finally G0=111. Among 43 analyzed cases (G01), 13 persons were in the seroconversion phase (both positive IgM>1.0 AU/ml and IgG>0.2 AU/ml), 30 persons were in a late phase producing secondary antibodies (positive IgG, negative IgM), but eight persons were in an early phase of the humoral viral response (positive IgM, negative IgG).
Our study materials were blood specimens taken through venepuncture sampling. The concentration of antibodies was evaluated 4 hours after blood collection. If the immediate assessment was not possible, the serum was collected and stored at -80 °C.
All 1063 participants had elevated levels of IgM and IgG antibodies oriented specifically towards SARS CoV-2; in 546 subjects, IgG anti-S (S-RBD) antibodies we detected by chemiluminescent immunoassay-CLIA (MAGLUMI, Snibe Diagnostic, Shenzhen China).
The results were greater or equal to 1.0 AU/ml SARS CoV-2 IgG, IgM, and S-RBD we considered reactive and recognized as positive according to the manufacturer's protocol.
Of the study participants, 827 were vaccinated, including Comirnaty 787 persons. BNT162b2 was 95% effective in preventing COVID-19, and similar vaccine efficacy observes across subgroups defined by age, sex, race, ethnicity. Table 2 is data on gender and age supplement to Table 1.
The Bioethics Commission of Medical University gave consent for our research.
3. Statistical analysis
Nonparametric statistical methods we applied for the case-control analyses because of a lack of considered variables with a normal distribution. Comparing two groups to each other, the Mann-Whitney test was adopted, whereas the Kruskal-Wallis test was applied to assess more than two groups. The statistically actual results were assumed to be p<0,05: We used PQStat Software 2021 and Tibco statistic 13.3.