The Objectives of This Study Are Comparative Assessment of the Tolerability, Safety and Immunogenicity of the Flu-M Vaccine vs. the Ultrix® Vaccine by Single Vaccination of Children Aged 6 to 17 Years.

Inclusion Criteria: For volunteers aged 12 to 17 years: * Healthy children1 of both sexes aged 12 to 17 years (12 years 0 months 0 days - 17 years 11 months 30 days); * The written and dated informed consent of the volunteer (children aged 14-17 years) one of the parents 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 mensis in the medical history shall have a negative pregnancy test result. For volunteers aged 6 to 11 years: * Healthy children of both sexes aged 6 to 11 years (6 years 0 months 0 days - 11 years 11 months 30 days); * The written and dated informed consent of one of the parents for participation in the trial; For all volunteers: • Ability of a volunteer / volunteer's parents to fulfill the requirements of the Protocol (i.e. to fill out the Patient Diary, come to visit with the volunteer) Exclusion Criteria: History of influenza or previous influenza vaccination during 6 months before the trial; * 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; * A serious post-vaccination reaction (temperature above 40 °C, hyperemia or edema more than 8 cm in diameter) 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); * Allergic reactions to vaccine components or any previous vaccination; * History of allergic reaction to chicken protein; * Encephalopathy that developed within 7 days of a previous vaccine administration; * History of hematopoietic system, cancer; * Carriage of HIV, syphilis, hepatitis B and C in the medical history, including by parents; * Children who received immunoglobulin products or transfusions of whole blood or its components less than 3 months before the start of the trial; * Long-term use (for more than 14 days) of any immunomodulating drugs (immunoregulating peptides, cytokines, interferons, immune system effector proteins (immunoglobulins), interferon inducers (cycloferon)) less than 3 months prior to the commencement of the trial; * Any confirmed or suspected immunosuppressive or immunodeficiency condition; * 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; * History of progressive neurological pathology, convulsive syndrome, afebrile convulsions; * Acute infectious or non-infectious diseases less than 2 weeks before vaccination; * Participation in another clinical trial less than 3 months before the start of the trial; * Smoking (for children of older age group); * Drug or alcohol abuse in the medical history (for children of older age group); * Serious concurrent illnesses or pathological conditions not listed above which, in the opinion of the investigator, could complicate the assessment of the results of the trial including pathological deviations from age norms and norms of laboratory blood and urine parameters, which are clinically significant in the opinion of the investigator, or which may be a counter-indicative to participation in the trial in the opinion of the investigator; * History of mental illness of the volunteer's parents