Introduction: Lack of comparative studies on efficiency of a broad range of COVID19 vaccines leads to lower levels of adoption and subsequent lower total immunity in several regions, including Republic of Belarus. This clinical study captures and transparently demonstrates varying immunogenic responses to Sputnik V and Sinopharm vaccines. Aim of this study was: to compare the immunogenicity and reactogenicity of Sputnik V (Gam-COVID-Vac), RF and Sinopharm (BBIBP-CorV), PRC vaccines in vaccinated individuals. Materials and Methods: A total of 60 adults participated the study. The immune response after vaccination was assessed using enzyme immunoassay. IgG levels measured in all participants at three time points: before the vaccination, 42 days after the first vaccine dose, and 6 months after the first vaccine dose. The results of the SARS-CoV-2 antibody test is quantified according to the WHO First International Standard (NIBSC code:20/136) and expressed in international units (BAU/ml). Results: The study participants were divided into two groups, where 30 people (50%) were vaccinated with Sputnik V (Gam-COVID-Vac), and 30 people were vaccinated with Sinopharm (BBIBP-CorV), with no gender differences in the groups. The IgG levels at 42 days after the first vaccine dose were: Sputnik V (Gam-COVID-Vac)(42 days): Me=650.4 (642.2-669.4); Sinopharm (BBIBP-CorV)(42 days): Me=376.5 (290.9-526.4); p<0,001). The IgG levels at 6 months after the first vaccine dose were: Sputnik V (Gam-COVID-Vac)(6 months) Me=608.7 (574.6-647.1); Sinopharm (BBIBP-CorV)(6 months): Me=106.3 (78.21-332.4); p<0,001). Reactions after vaccination appeared in 27 vaccinated individuals (45%). Conclusion: The study showed that Sputnik V (Gam-COVID-Vac) vaccine was more immunogenic than Sinopharm (BBIBP-CorV) vaccine. IgG levels in vaccinated individuals who previously recovered from SARS-CoV-2 infection ("hybrid immunity") were higher than in SARS-CoV-2 naive individuals. Reactions after vaccines administration were mild to moderate.

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Relevance. Many countries around the world are developing effective vaccines against SARS-CoV-2. The measure of the effectiveness of the vaccination process has traditionally been antibody production. The frequency and intensity of adverse reactions is also an important factor in making a decision regarding a vaccine. This study presents the results of the evaluation of the formation of humoral immunity and the occurrence of reactions in response to the administration of Sputnik V (Gam-COVID-Vac), RF, and Sinopharm (BBIBP-CorV), PRC. Aim. Analyze immunogenicity and reactogenicity of COVID-19 vaccines used in the Republic of Belarus (Sputnik V and Sinopharm). Materials and methods. Evaluation of postvaccination immune response by enzyme immunoassay and differential enzyme immunoassay for class G immunoglobulins to S- and N-proteins SARS-CoV-2. Blood plasma of the study participants was used as biological material. Blood sampling was performed 3 times: immediately before the first vaccine dose, on day 42, and 6 months after the first vaccine dose. To evaluate the frequency and intensity of postvaccination reactions, study participants were questioned. Results. At 42 days after administration of both vaccines, antibody levels are rising, with a significantly higher quantitative IgG count for the Sputnik V vaccine. This trend is also observed 6 months after the first dose of both vaccines, both among those previously infected with SARS-CoV-2 and those without a history of COVID-19. The comparison of Sputnik V and Sinopharm vaccine groups in terms of IgG (BAU/ml) levels to S- and N-proteins revealed a statistically significant difference in IgG levels to S-protein: the Sputnik V vaccine group had significantly higher IgG levels to S-protein than the Sinopharm vaccine group (p = 0.0000196). The incidence of adverse reactions in this study was 45%. All reactions noted were mild to moderate in severity. The most common were soreness and redness at the injection site, elevated body temperature, and a combination of several reactions. The increased body temperature after vaccination was more common among those vaccinated with the Sputnik V vaccine. Conclusion. Compared to Sinopharm, Sputnik V vaccine produces higher antibody level. Adverse reactions were observed in both vaccinated groups. However, significant statistical differences were found with regard to fever in the Sputnik V vaccine group, which occurred more frequently.

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This paper reviews modern literature and presents a brief analysis of our own data on one of the most pressing issues in modern transplantology and, in particular, transplant hepatology – the role and place of gut-liver axis (GLA) in the early post-transplant period. Objective: to compare the correlation between gut microbiome palette and incidence of certain early postoperative complications in liver transplantation. Materials and methods. The study design is presented as a pilot, prospective, observational, double-blind study based on investigation of the composition of the microbiome residing in the large intestinal in patients that underwent orthotopic liver transplantation (OLTx). The primary cohort of patients consisted of 12 patients who underwent OLTx from a postmortem donor. To assess the gut microbiome palette, biomaterial was collected from all patients in the preand post-transplant period followed by next-generation sequencing. The study was conducted as primary study results registered under number NCT04281797. Results. In the preoperative period, differences close to statistically reliable in relation to Actinobacteria were observed in patients included in the liver transplant waiting list for cirrhosis (LC) and hepatocellular carcinoma (HCC) in cirrhosis. However, due to the pilot nature of the study, this study cohort was limited to an extremely small sample. In turn, in the post-transplant period, there was a statistically significant difference in the taxonomic range of Actinobacteria (p < 0.05) between the above groups, indicating a possible effect of liver transplantation on the gut microbiome. In addition, in the early post-transplant period, there was a marked difference in the microbiome palette between patients with and without acute cellular rejection. Conclusion. GLA and the gut microbiome play a critical role in many liver diseases, and may also have a significant impact on the post-transplant period. In this regard, further research in this direction will not only characterize the predictors and risk factors of bacterial infection and rejection episodes, but will also allow us to form a completely new approach to the treatment tactics for certain complications, including through formation of a microbiota-oriented pharmacotherapy.