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Introduction. The large-scale and prolonged pandemic of the novel coronavirus disease (COVID-19) has demonstrated the need for effective vaccination. Along with immunogenicity, safety is a critical issue for vaccines, as public trust can contribute to the success or failure of immunization programs. In preclinical studies, we assessed the safety of an intranasal Virus-like particle (VLP)-based vaccine in mice and rats.

The aim of the study is to conduct preclinical acute and subchronic toxicity studies assessing local tolerability of an intranasal VLP vaccine against COVID-19 in accordance with good laboratory practice.

Materials and methods. Study was performed on adult outbreed mice (30 males, 30 females) and rats (45 males, 45 females). Physiological, morphometric and histological parameters, as well as general and biochemical blood tests and urine analysis were assessed.

Results. No deaths or intoxication were recorded in the acute toxicity study on mice, all parameters were within the physiological norm. In the subchronic toxicity study on rats, no changes in the general condition, behavior, or death of animals were noted. The structure of internal organs, blood and urine tests, hemostasis did not differ significantly between the groups. No local irritant effect was detected at the injection site during visual assessment, cytological and histological analysis.

Conclusion. The VLP vaccine is safe, as evidenced by the results of preclinical studies, does not negatively affect the function of various organs, the level of cellular and biochemical biomarkers in the blood and urine of mice and rats. Visual assessment, cytology and histology of the vaccine injection site did not reveal any local irritant effect.