Safety of a Single Dose or Two Doses of Shenzhen Quadrivalent Influenza Vaccine

Inclusion Criteria: * Aged ≥ 6 months on the day of inclusion * For participants aged 6 months through 17 years: Informed consent form has been signed and dated by the parent(s) or another legally acceptable representative, if applicable. Additionally an assent form has been signed and dated by the participant if aged 8 through 17 years (based on local regulations) For participants aged 18 years and older: Informed consent form has been signed and dated by the participant * Participant / Participant and parent/legally acceptable representative are able to attend all scheduled visits and to comply with all trial procedures * For participants aged less than 2 years only: Born at full term of pregnancy (≥37 weeks) and with a birth weight ≥ 2.5 kg Exclusion Criteria: * Participant is pregnant, or lactating, or of childbearing potential and not using an effective method of contraception or abstinence from at least 4 weeks prior to vaccination until at least 4 weeks after vaccination. To be considered of non-childbearing potential, a female must be pre-menarche or post-menopausal for at least 1 year, surgically sterile * Participation at the time of study enrollment (or in the 4 weeks preceding the trial vaccination \[or the first trial vaccination\]) or planned participation during the present trial period in another clinical trial investigating a vaccine, drug, medical device, or medical procedure * Receipt of any vaccine or planned receipt of any vaccine within the period from 4 weeks before study vaccination (or the first study vaccination) to 4 weeks following study vaccination (or the last study vaccination) * Previous vaccination against influenza with either the study vaccine or another vaccine from the current season * Receipt of any vaccine or planned receipt of any vaccine within the period from 2 weeks before trial vaccination (or the first trial vaccination) to 2 weeks following trial vaccination (or the last trial vaccination) * For participants aged 6 to 8 years only: Previous vaccination against influenza vaccine in the past * For participants aged 9 years and older: Previous vaccination against influenza (in the previous 6 months) with either the trial vaccine or another vaccine * Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy, within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months) * Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances * Self-reported thrombocytopenia or known thrombocytopenia as reported by the parent/legally acceptable representative, contraindicating IM vaccination * Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating IM vaccination * Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily * Current alcohol abuse or drug addiction * Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion * Moderate or severe acute illness/infection (according to investigator judgment) on the day of vaccination or febrile illness (axillary temperature ≥ 37.1°C). A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided. * Identified as an Investigator or employee of the Investigator or study center with direct involvement in the proposed study, or identified as an immediate family member (i.e., parent, spouse, natural or adopted child) of the Investigator or employee with direct involvement in the proposed study