The primary objectives of the study are:

• To describe the safety profile of the different quadrivalent recombinant influenza vaccine (RIV) formulations.
• To describe the hemagglutination inhibition (HAI) and seroneutralization (SN) antibody responses against hemagglutinin (HA) (H1, H3, B/Victoria, and B/Yamagata) antigens present in the control vaccine in all groups at all timepoints.

The secondary objectives of the study are:

• To describe antigenic coverage in each group by assessing the HAI and SN antibody responses against a panel of H3 antigens (not present in any of the vaccine formulations).
• To describe HAI and SN antibody responses in each group against each of the H3 antigens.
• To compare the HAI and SN antibody responses for the groups with different H3 antigens to the control group.

Study duration per participant is approximately 90 days.

Inclusion criteria :

• Aged 18 to 30 years on the day of inclusion
• Informed consent form has been signed and dated
• Able to attend all scheduled visits and to comply with all study procedures

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 12 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 4 weeks preceding the study vaccination) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure
• Receipt of any vaccine in the 4 weeks preceding the study vaccination or planned receipt of any vaccine in the 4 weeks following study vaccination
• Previous vaccination against influenza in the previous influenza season (2018-2019) with any licensed or investigational influenza vaccine
• Previous vaccination against influenza in the 2019-2020 season with any licensed influenza vaccine
• Receipt of immune globulins, blood or blood-derived products in the past 3 months
• 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)
• Have known active or recently active (12 months) neoplastic disease or a history of any hematologic malignancy
• History of influenza infection during the 2018-2019 or 2019-2020 influenza season, confirmed by laboratory tests (including rapid tests)
• Self-reported or documented seropositivity for human immunodeficiency virus, hepatitis B, or hepatitis C
• Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccines used in the study or to a vaccine containing any of the same substances
• Thrombocytopenia or bleeding disorder, contraindicating intramuscular vaccination based on Investigator's judgement
• Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily
• Alcohol abuse or substance abuse that, in the opinion of the investigator, might interfere with the study conduct or completion
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion or predispose to complications associated with influenza infection
• Have any diagnosis, current or past, of chronic pulmonary diseases including asthma, cystic fibrosis and chronic pulmonary obstructive disease
• Have taken high-dose inhaled corticosteroids within 6 months prior to study vaccination
• Body Mass Index of 40 or higher
• History of cardiac disease such as congenital heart disease, heart failure, coronary artery disease (except isolated hypertension)
• Health care personnel in inpatient and outpatient care settings, medical emergency-response workers, employees of nursing home and long-term care facilities who have contact with patients or residents and students in these professions who will have contact with patients
• Moderate or severe acute illness/infection (according to investigator judgment) on the day of vaccination or febrile illness (temperature ≥ 100.4 F [≥ 38.0 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 (ie, parent, spouse, natural or adopted child) of the Investigator or employee with direct involvement in the proposed study
• Personal or family history of Guillain-Barré syndrome

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org