- To demonstrate the non-inferiority of the vaccine seroresponse of meningococcal serogroups A, C, Y, and W following the administration of a booster dose of MenACYW conjugate vaccine compared to those observed following the administration of a booster dose of a licensed Meningococcal Conjugate Vaccine (MCV4) in subjects who were first vaccinated with 1 dose of MCV4, 4 to 10 years before the booster dose.