The goal of this clinical trial is to assess tolerability, reactogenicity, safety and immunogenicity of the Flu-M Tetra vaccine as compared to the VaxigripTetra vaccine in terms of prevention of influenza in children aged 6 months to 17 years old inclusive.

The trial will be conducted in three stages.

• Stage I Participants - children aged 10 to 17 years (10 years 0 months 0 days - 17 years 11 months 30 days), will be vaccinated a single 0.5 mL dose of the Flu-M Tetra vaccine or the VaxigripTetra vaccine intramuscularly.

Once reviewed by the Sponsor, the report will be submitted to the supervisory executive authorities alongside the notice of commencement of Stage II trial.

• Stage II Participants - children aged 3 to 9 years (3 years 0 months 0 days - 9 years 11 months 30 days), will be vaccinated a single 0.5 mL dose of the Flu-M Tetra vaccine or the VaxigripTetra vaccine intramuscularly (double dose for volunteers who have not been vaccinated before).

Once reviewed by the Sponsor, the report will be submitted to the supervisory executive authorities alongside the notice of commencement of Stage III trial.

• Stage III Participants - children aged 6 to 35 months (6 months 0 days - 35 months 30 days), will be vaccinated twice 0.25 mL dose of the Flu-M Tetra vaccine or the VaxigripTetra vaccine intramuscularly.

Inclusion Criteria:

For volunteers aged 10 to 17 years:

• Healthy children of both sexes aged 10 to 17 years (10 years 0 months 0 days - 17 years 11 months 30 days);
• The availability of written and dated informed consent of the volunteer (children aged 14 to 17 years) and their parent / legally acceptable representative for participation in the trial;
• If the volunteer has sexual relations, effective contraception methods must be used during the 30 days preceding vaccination and consent must be obtained to continue using these contraceptive methods during the trial and for two months after vaccination;
• The girls with menses in the medical history shall have a negative pregnancy test result.

For volunteers aged 3 to 9 years:

• Healthy children of both sexes aged 3 to 9 years (3 years 0 months 0 days - 9 years 11 months 30 days);
• The availability of written and dated informed consent of a parent / legally acceptable representative for participation in the trial;

For volunteers aged 6 to 35 months:

• Healthy children of both genders aged 6 to 35 months, inclusive (6 months 0 days - 35 months 30 days);
• The availability of written and dated informed consent of a parent / legally acceptable representative for participation in the trial.
• The trial subject of the was born full-term, with the Apgar score of 7-10 points.

For all volunteers:

The ability of a volunteer's parents / legally acceptable representatives to perform the requirements of the Protocol (i.e., fill out the Patient Diary, attend visits together with the volunteer).

Exclusion Criteria:

1. History of influenza (including in mothers for children aged 6 to 35 months) or previous influenza vaccination during 6 months before the trial;
2. Vaccination of the pregnant woman in the 2nd-3rd trimester (for the age group of 6 - 35 months) with an influenza vaccine
3. Positive result of the SARS-CoV-2 test;
4. Vaccination with any vaccine less than 30 days before participating in the trial or scheduled vaccination with any vaccine within 30 days after vaccination with the trial vaccines;
5. A serious post-vaccination reaction (temperature above 40 °C, hyperemia or edema more than 8 cm in diameter at the injection site) or complications (collapse or shock-like condition that developed within 48 hours after vaccination; convulsions accompanied or not accompanied by a fever due to any previous vaccination), encephalopathy;
6. Allergic reactions to vaccine components or any previous vaccination;
7. History of allergic reaction to chicken protein;
8. History of cancer, leukemia, tuberculosis, autoimmune diseases;
9. Carriage of HIV, syphilis, hepatitis B and C in the medical history, including by parents / legally acceptable representatives;
10. Children who received immunoglobulin products or transfusions of whole blood or its components less than 3 months before the start of the trial;
11. Long-term use (more than 14 days) of any immunomodulating medicines less than 3 months before the start of the trial;
12. Any confirmed or suspected immunosuppressive or immunodeficiency condition;
13. History of chronic diseases of the cardiovascular, bronchopulmonary, endocrine systems, blood in the acute stage (recovery less than 4 weeks before vaccination) or in the decompensation stage;
14. Children with hemophilia who may develop bleeding after intramuscular injection;
15. History of progressive neurological pathology, convulsive syndrome, afebrile convulsions;
16. History of acute infectious diseases (fever ≥ 37.5°С): recovery less than 2 weeks before vaccination;
17. Participation in another clinical trial less than 3 months before the start of the trial;
18. History of mental illness of the child and the volunteer's parents;
19. The history of the volunteer's parent / legally acceptable representative being registered with a tuberculosis dispensary and/or a narcological dispensary;
20. Maternal history of drug use or alcohol abuse during pregnancy and/or breastfeeding;
21. Pronounced congenital malformations in a child;
22. Suspected developmental delay in a child.