Funding: the study was supported by the major Sistema BioTech LLC shareholder, the Sistema Public Joint Stock Financial Corporation. The study was funded by the Moscow Department of Health as part of the double blind clinical trial.

Acknowledgements: the authors express their gratitude to Antipova YuO, Deputy Head of the Moscow Department of Health, for organizing the blind clinical trial of COVID-19 severity and the patients of the Diagnostic Center (Center of Laboratory Testing) of the Moscow Department of Health for the provided biomaterial samples.

Author contribution: Pozdnyakova NV, Poyarkov SV — study concept and design; Minashkin MM — molecular genetic research, laboratory tests; Poyarkov SV, Traspov AA — literature review, manuscript writing; Traspov AA — statistical processing of the results, manuscript editing; Komarov AG — project management, planning the experiment, data analysis; Shtinova IA, Speshilov GI, Karbyshev IA — providing clinical data and metadata; Godkov MA — control over clinical sample collection at the Sklifosovsky Research Institute for Emergency Medicine, providing anonymized data.

Compliance with ethical standards: the study did not need to be approved by the Ethics Committee because of dealing with anonymized patient data and the double blind study format.