Safety and Immunogenicity of Fluzone® Quadrivalent and Fluzone® High-Dose, Influenza Vaccines

Inclusion Criteria: * Aged 6 months to \< 9 years or ≥ 18 years on the day of first study vaccination (study product administration). * For participants 6 to \< 12 months of age, born at full term of pregnancy (≥ 37 weeks) and with a birth weight ≥ 2.5 kg (5.5 lbs). * Informed consent form has been signed and dated by participants ≥ 18 years of age. * Assent form was signed and dated by participants 7 to \< 9 years of age, and informed consent form has been signed and dated by parent(s) or guardian(s) for participants 6 months to \< 9 years of age. * Participant and parent/guardian (of participants 6 months to \< 9 years of age) were able to attend all scheduled visits and to comply with all study procedures. Exclusion Criteria: * Participant was 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 and 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, or surgically sterile. * Participation at the time of study enrollment (or in the 30 days preceding the first study vaccination) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure. Note: Participants may be considered eligible for enrollment if no intervention for the other study occurred within the 30 days prior to the first study vaccination and none are planned before the participant would complete safety surveillance for the present study. * Receipt of any vaccine in the 30 days preceding the first study vaccination, or planned receipt of any vaccine before Visit 2 for participants receiving 1 dose of influenza vaccine or Visit 3 for participants receiving 2 doses of influenza vaccine. * Previous vaccination against influenza (in the 2017-2018 influenza season) with either study vaccine or another vaccine. * Receipt of immune globulins, blood, or blood-derived products in the 3 months preceding planned inclusion. * Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy, within the 6 months preceding planned inclusion; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the 3 months preceding planned inclusion). * Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to study vaccine or to a vaccine containing any of the same substances. Note: The list of vaccine components is included in the Prescribing Information for each study vaccine. * Thrombocytopenia, which may be a contraindication for intramuscular vaccination, at the discretion of the Investigator. * Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating intramuscular 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, was at a stage where it might interfere with study conduct or completion. * Moderate or severe acute illness/infection (according to Investigator judgment) on the day of planned vaccination or febrile illness (temperature ≥ 100.4 degree Fahrenheit \[°F\] \[38.0 degrees Celsius {°C}\]). 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 (participants ≥ 18 years of age) 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 (all participants). * History of serious adverse reaction to any influenza vaccine. * Personal history of Guillain-Barré syndrome. * Any condition that in the opinion of the Investigator would pose a health risk to the participant if enrolled or could interfere with the evaluation of the vaccine. * Personal history of clinically significant developmental delay (at the discretion of the Investigator), neurologic disorder, or seizure disorder. * Known seropositivity for human immunodeficiency virus, hepatitis B, or hepatitis C.