In summary, participants enrolled in this study will have a total of 5 visits in a period of 2 months. They will receive two doses of the MenACWY conjugate vaccine or one dose of the ACWY polysaccharide vaccine followed by one dose of the MenACWY conjugate vaccine. During this period they will have a total of 5 blood samples taken (5x20mL= 100 mL of blood taken in a 2 month period).