Co-administration of an investigational quadrivalent meningococcal serogroups A , C , W and Y tetanus toxoid conjugate vaccine ( MenACWY-TT ) with the fourth dose of diphtheria-tetanus-acellular pertussis vaccine ( DTaP ) at age 15-18 months was investigated in 3-dose Haemophilus influenzae type b-meningococcal serogroups C/Y conjugate vaccine ( HibMenCY-TT ) - primed toddlers .