Morbidity surveys in certain regions during the COVID-19 pandemic have established that the infection spreads in a wave-like manner characterised with peaks and troughs in incidence. According to the analysis of COVID-19 epidemic development in Russia, surges in COVID-19 infections are mainly driven by seasonal factors, insufficient herd immunity, and emerging SARS-CoV-2 variants with increased transmissibility. The aim of the study was to analyse environmental, biological and social factors contributing to new rises in COVID-19 cases in Russia. The study covers the global epidemiological situation as of mid-2022 and the role of environmental, biological, and social factors in the spread of COVID-19 in the Russian Federation. The results suggest that new highly contagious SARS-CoV-2 variants and seasonality are the principal factors driving new rises in morbidity. The authors assume that the sixth and the seventh COVID-19 waves in Russia will be in line with the best case scenario, which predicts the spread of a SARS-CoV-2 variant with increased transmissibility and reduced virulence.

At the end of 2019, an outbreak of a new coronavirus began in the city of Wuhan (Hubei Province) in the People's Republic of China. The outbreak turned into a pandemic. In the shortest possible time, national and international manufacturers developed preventive COVID-19 vaccines, and the population was vaccinated. During pandemics, accelerated approval of vaccines is an important factor that shortens the time to market with the aim of mass vaccination. The experience of rapidly developing and introducing vaccines into routine practice is not only important for managing the current pandemic, but also valuable in case of extremely likely future ones. The aim of this study was to analyse the main issues associated with assessing the safety and efficacy of vaccines for COVID-19 prevention during their registration and widespread use amid the pandemic and ongoing SARS-CoV-2 evolution. The vaccines for COVID-19 prevention were developed and introduced into healthcare practice very rapidly and under the circumstances of the pandemic, and the use of these vaccines has surfaced a number of concerns requiring further research. The most important issues identified in the performed analysis include, but are not limited to the need for accelerated assessment of the safety and immunogenicity of new vaccines; the lack of immune correlates of protection against SARS-CoV-2; the waning of antibody immunity over time, motivating the need to determine revaccination and post-recovery vaccination timelines; and the emergence of mutant SARS-CoV-2 variants. One of noteworthy aspects is the need to develop recommendations for updating the strain composition of registered COVID-19 vaccines. According to the conclusions, the level of herd immunity, including vaccine-induced protection, plays a certain role in virus evolution during the pandemic. If COVID-19 becomes seasonal, which is a probable scenario, regular revaccination can be essential.

The COVID-19 pandemic has presented a global challenge to the health system. More than 200 years of world epidemiological experience since the first mass use of vaccines have convincingly shown that effective vaccines are the key tools in the fight against dangerous infectious diseases, especially epidemic and pandemic ones. In the context of a rapidly spreading pandemic of a new infectious agent, it is crucial not only to develop fundamentally new vaccines, but also to be able to quickly organise their large-scale production. In the Russian Federation, in 2020, a team of the National Research Centre for Epidemiology and Microbiology named after Honorary Academician N.F. Gamaleya developed an innovative vector vaccine, Gam-COVID-Vaс, for the prevention of coronavirus disease caused by the SARS-CoV-2 virus. A number of pharmaceutical companies faced the challenge of producing the vaccine. The aim of the study was to optimise the production technology of Gam-COVID-Vac for scaling and increasing the production capacity. In the course of the work, the authors established critical quality attributes of the product, optimised analytical methods for their control, identified poorly scalable technological stages, streamlined the technological process before its transfer to production, and modified non-scalable and technologically unfeasible stages. The work resulted in the launch of industrial-scale production of active pharmaceutical ingredients for both components of Gam-COVID-Vac, which made it possible not only to meet the critical need for COVID-19 immunoprophylaxis in the Russian Federation, but also to supply this vaccine to a number of foreign countries.

The development of COVID-globulin, a COVID-19-specific human immunoglobulin preparation, involved choosing a method to quantify antibodies to SARS-CoV-2. Antibody titre determination by virus neutralisation (VN) is labour-intensive and unsuitable for large-scale application. To enable routine testing, it was necessary to develop a less demanding method; the enzyme-linked immunosorbent assay (ELISA) was the most appropriate of solutions. The lack of international and industry reference standards (RS) prompted the preparation and certification of an RS for COVID-globulin potency control.

The aim of the study was to examine the possibility of substituting ELISA for VN and to develop an RS for SARS-CoV-2 antibody quantification in immunoglobulin preparations.

Materials and methods: the authors used commercial ELISA kits by several manufacturers, COVID-globulin by Microgen (48 batches), and human plasma samples from multiple sources (1499 samples). The tests were performed by VN, ELISA, and chemiluminescent microparticle immunoassay.

Results: the authors validated an ELISA method for SARS-CoV-2 antibody quantification with the selected reagent kits by the National Medical Research Center for Hematology (NMRC for Hematology) and Euroimmun AG. The authors demonstrated the possibility of using ELISA instead of VN (with a correlation coefficient of more than 0.9). They developed and characterised an in-house RS for SARS-CoV-2 antibody content in human immunoglobulin preparations. The RS was certified in newly introduced anti-COVID units (ACU) and in international binding antibody units (BAU) using the World Health Organisation (WHO) international reference panel (NIBSC code: 20/268). The RS's potency was measured in terms of its neutralising activity in ACU (320 ACU/mL) and BAU (2234.8 BAU/mL). The authors established the relationship between ACU and BAU units. For the selected ELISA reagent kits, the conversion factors were 6.4 (NMRC for Hematology) and 7.0 (Euroimmun AG).

Conclusions: the ELISA method for SARS-CoV-2 antibody quantification and the RS for SARS-CoV-2 antibody content can be applied to determine the potency of human anti-COVID-19 immunoglobulins.

The severe consequences and high mortality of COVID-19 prompted the development of a wide range of preventive vaccines. The first vaccines to be tested were developed in China and formulated as inactivated SARS-CoV-2 adsorbed on aluminium hydroxide. One of the quality indicators for inactivated adsorbed vaccines is the degree of adsorption, which can be used to control the content not only of non-adsorbed antigen, but also of specific antigen in one dose of a vaccine.

The aim of the study was to investigate the possibility of desorbing SARS-CoV-2 antigen from formulated adsorbed vaccines and the possibility of measuring its concentration using the BioScan-SARS-CoV-2 (S) ELISA kit for SARS-CoV-2 S-protein content determination.

Materials and methods: the study used four batches of BBIBP-CorV by CNBG, Sinopharm (China) and three batches of CoronaVac by Sinovac Biotech (China). The authors desorbed SARS-CoV-2 S antigen in accordance with monograph FS.3.3.1.0029.15 of the State Pharmacopoeia of the Russian Federation (Ph. Rus.), edition XIV, and quantified it using the BioScan-SARS-CoV-2 (S) ELISA kit by Bioservice Biotechnology Co. Ltd. (Russia).

Results: mean S-antigen concentrations in the desorbed samples ranged from 61 to 129 ng/mL for BBIBP-CorV and from 461 to 533 ng/mL for CoronaVac.

Conclusions: the study demonstrated the possibility of specific SARS-CoV-2 antigen desorption from the surface of aluminium hydroxide using the Ph. Rus. method, as well as the possibility of S-antigen quantification in desorbed medicinal products and supernatants using the BioScan-SARS-CoV-2 (S) ELISA kit. The authors observed 3.6- to 8.7-fold difference between the S-antigen concentrations of the desorbed preparations by the two manufacturers.

Finding effective and safe medicines to fight SARS-CoV-2 infection is an urgent task. RPH-137 is an original trap fusion protein against SARS-CoV-2 virus. It comprises the angiotensin-converting enzyme type 2 extracellular domain and the human IgG1 Fc fragment.

The aim of the study was to carry out a preclinical evaluation of the efficacy of RPH-137 and molnupiravir against SARS-CoV-2 infection.

Materials and methods: the authors analysed RPH-137 expressed in a stable CHO cell line and molnupiravir used as an active pharmaceutical ingredient. Drug-mediated inhibition of virus-induced cytotoxicity was assessed in Vero cell culture. In vivo efficacy assessments were performed in Syrian hamsters. The animals were infected intranasally with SARS-CoV-2 (PIK35 clinical isolate) in the dose of 5 log TCID₅₀. The authors evaluated body weight measurements, lung–body weight ratios, and lung histopathology findings and determined viral RNA levels in oropharyngeal swabs by RT-PCR using the amplification cycle threshold (Ct). The statistical analyses involved one- and two-way ANOVA, Student's t-test, and Mann–Whitney test.

Results: RPH-137 and molnupiravir inhibited the cytopathic effect of SARS-CoV-2 in Vero cells; the EC₅₀ values of RPH-137 amounted to 4.69 μg/mL (21.3 nM) and 16.24 μg/mL (73.8 nM) for 50 TCID₅₀ and 200 TCID₅₀, respectively, whereas the EC₅₀ values of molnupiravir were 0.63 μg/mL (1900 nM) for both doses. Intramuscular RPH-137 (30 and 80 mg/kg) had no effect on the infection process in Syrian hamsters. The comparison with the challenge control group showed that intraperitoneal RPH-137 (100 mg/kg) had statistically significant effects on a number of parameters, including a 27% reduction in inflammation and a 30% reduction in the total lesion area of the lungs by Day 7. Intragastric molnupiravir (300 mg/kg twice daily) significantly inhibited SARS-CoV-2 infection.

Conclusions: both RPH-137 and molnupiravir inhibited the cytopathic effect of SARS-CoV-2 in Vero cells. In Syrian hamsters, molnupiravir demonstrated a more pronounced inhibition of SARS-CoV-2 infection than RPH-137. However, RPH-137 had statistically significant effects on a range of parameters. This offers additional perspectives for further research.

In November 2020, the Armed Forces of the Russian Federation began mass immunisation of the personnel with Gam-COVID-Vac (Sputnik V), the first Russia vaccine against the new coronavirus infection (COVID-19). Thus, it became necessary to assess post-vaccination antibody levels and the duration and intensity of humoral immunity to COVID-19.

The aim of the study was to investigate the immunogenicity and efficacy of Gam-COVID-Vac in military medical staff after vaccination.

Materials and methods: the authors determined the presence of specific antibodies in the serum of individuals immunised with Gam-COVID-Vac (477 volunteers) and COVID-19 convalescents (73 patients), using virus neutralisation (VN), enzyme-linked immunosorbent assay (ELISA) with reagent kits by several manufacturers, and immunoblotting. The results of the study were evaluated using analysis of variance.

Results: VN detected virus neutralising antibodies in 90.7% of vaccinated subjects; ELISA, in 95.4%. Both VN and ELISA showed lower antibody levels in the vaccinated over 50 years of age. ELISA demonstrated a significantly higher concentration of anti-SARS-CoV-2 spike IgG in the Gam-COVID-Vac group than in the COVID-19 convalescent group. The correlation between antibody detection results by VN and ELISA was the strongest when the authors used their experimental reagent kit for quantitative detection of virus neutralising antibodies by competitive ELISA with the recombinant human ACE2 receptor. Having analysed the time course of neutralising antibody titres, the authors noted a significant, more than two-fold decrease in geometric means of the titres three months after administration of the second vaccine component.

Conclusions: the subjects vaccinated with Gam-COVID-Vac gain effective humoral immunity to COVID-19. The decrease in titres indicates the need for revaccination in 6 months.

The COVID-19 mortality is associated with an increase in interleukin-6 (IL-6) levels. Levilimab is an anti–IL-6 receptor antibody with proven clinical efficacy in patients with severe COVID-19.

The aim of the study was to assess the association of COVID-19 severity and levilimab effectiveness with IL-6 levels and to explore the potential for using levilimab in other conditions accompanied by cytokine release syndrome.

Materials and methods: the subgroup analysis was based on the data of COVID patients with known baseline IL-6 levels from the CORONA clinical study. Subgroups were formed according to baseline IL-6 levels: ≤5 pg/mL (normal) and >5 pg/mL (elevated). The subgroup analysis included descriptive statistics of the patients and time courses of their clinical and laboratory findings (at screening, on the day of investigational product administration, and further until day 14). In order to compare the percentages of patients who had required rescue therapy, the authors used Fisher's exact test.

Results: the subgroup analysis included 91 patients (47 from the levilimab group and 44 from the placebo group). At baseline, the authors observed elevated levels of IL-6 in 31/47 (66%) subjects in the levilimab group and 29/44 (48.4%) subjects in the placebo group. The subjects with elevated IL-6 demonstrated more pronounced clinical signs of pneumonia and abnormalities in inflammatory markers. Elevated baseline IL-6 levels were associated with the need for rescue therapy (OR=3.714; 95% CI: 1.317–9.747; p=0.0183); this association was stronger in the placebo group (OR=8.889; 95% CI: 2.098–33.31; p=0.0036). Also, the placebo group showed long-term abnormalities in the clinical and laboratory findings.

Conclusions: IL-6 is one of the key elements in the pathogenesis of cytokine release syndrome related to COVID-19 and other conditions. Elevated IL-6 levels are associated with the severity of COVID-19. Inhibition of IL-6 receptors by levilimab leads to clinical improvement in patients with severe COVID-19, suggesting the effectiveness of levilimab in pathogenesis-oriented therapy for cytokine release syndrome of other aetiologies.