I am as a member of international team of involved scientists associated with the study of this vaccine in various roles, either as participants in this clinical trial, as specialists in clinical drug trial design, or as authors of articles examining the effectiveness of EpiVacCorona in retrospective studies as me, published in Vaccines, wish to express our serious concern about this publication. We are alarmed by the various multiple inconsistencies and ambiguities in the study. Moreover, to our knowledge, the general ability of this peptide-based vaccine to induce a virus-specific humoral response has never been conclusively demonstrated. Interestingly, Ryzhikov et al. completely ignored our recent publication in Vaccines and a published study by our colleagues, which in large retrospective study (1) or a test-negative case-control study (2) show the ineffectiveness of the EpiVacCorona vaccine.
1) Olga Matveeva and Alexander Ershov Retrospective Cohort Study of the Effectiveness of the Sputnik V and EpiVacCorona Vaccines against the SARS-CoV-2 Delta Variant in Moscow (June-July 2021). Vaccines (Basel). 2022;10(7).

2) Barchuk A, Bulina A, Cherkashin M, Berezina N, Rakova T, Kuplevatskaya D, et al. Gam-COVID-Vac, EpiVacCorona, and CoviVac effectiveness against lung injury during Delta and Omicron variant surges in St. Petersburg, Russia: a test-negative case-control study. Respir Res. 2022;23(1):276.

A more detailed critique of this article is outlined on Pubpeer in several comments below. Downloading the Pubpeer app to read the comments is not required.
(I) Statistical data analysis concerns

(II) Procedural concerns and CONSORT Guideline violation

(III) Incomplete description of outcomes

(IV) Study design, data presentation, and interpretation concerns

(V) General uncertainties in EpiVacCorona's virus-specific humoral induction