This study is conducted to support a 2-dose series (1+1 vaccination schedule) for immunization of individuals from 6 months of age. The study is designed to evaluate the non-inferiority of the immunological response of MenACYW conjugate vaccine to Nimenrix® after the completion of the 2-dose series (1+1 vaccination schedule), with the first dose (priming dose) being given at 6-7 months of age to MenACWY- naïve healthy infants and the second dose (booster dose) given at 12-13 months of age. This study will also describe additional immunogenicity parameters and safety of MenACYW conjugate vaccine and Nimenrix® in the same population of participants.

The study duration will be approximately 7 to 8.5 months (at least 7 months per participant).

Inclusion Criteria:

• Aged 6 to 7 months on the day of inclusion
• Participants who are healthy as determined by medical evaluation including medical history, physical examination and judgment of the Investigator

Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply:

• 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
• History of meningococcal infection, confirmed either clinically, serologically, or microbiologically
• At high risk for meningococcal infection during the study (specifically but not limited to participants with persistent complement deficiency, with anatomic or functional asplenia, or participants traveling to countries with high endemic or epidemic disease)
• Personal history of Guillain-Barré syndrome
• Personal history of an Arthus-like reaction after vaccination with a tetanus toxoid-containing vaccine
• Known systemic hypersensitivity to any of the study intervention components, or history of a life-threatening reaction to the study intervention(s) used in the study or to a product containing any of the same substances
• Moderate or severe acute illness/infection (according to investigator judgment) or febrile illness (temperature ≥ 38.0°C [≥ 100.4°F]) on the day of study intervention administration. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided
• Receipt of any vaccine (including COVID-19) and Meningococcal B vaccines) in the 4 weeks preceding the first and second study intervention administration or planned receipt of any vaccine (including COVID-19 and Meningococcal B vaccines) in the 4 weeks following any study intervention administration except for influenza vaccination, which may be received at least 2 weeks before or 2 weeks after the study interventions. This exception includes monovalent pandemic influenza vaccines and multivalent influenza vaccines.
• Previous vaccination against meningococcal A, C, W, or Y disease with either the trial vaccine or another vaccine (i.e., mono- or quadrivalent meningococcal conjugate vaccine) containing serogroups A, C, Y, or W.

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

The study will be performed in a modified double-blind fashion:

• Investigators and study staff who conduct the safety assessment, and the participants parent/ legally acceptable representative will not know which study intervention is administered
• Only the study staff who prepare and administer the study intervention and are not involved with the safety evaluation will know which study intervention is administered