Baseline Characteristics Study Population.

a. All participants were primed with one vaccination with the Meningococcal serogroup C polysaccharide conjugated to tetanus toxoid vaccine (MenC-TT, Baxter) and received a booster with the same vaccine at the beginning of the study (T0). Individual immunization histories were verified by checking personal vaccination cards or from centralized immunization records. b. Intervals slightly differed between groups (separate t-tests; P<0.001). Further testing showed no relation between interval duration and antibody levels (data not shown). Analyses were therefore not adjusted for this interval.