The safety and immunogenicity of MenACWY-CRM in children aged 2 through 10 years was evaluated in a multicenter, randomized controlled trial.1 A human complement serum bactericidal assay (hSBA) was used to measure antibody responses. Following a single MenACWY-CRM dose, seroresponses to group C, Y, and W-135 in children aged 2 through 5 years and 6 through 10 years were noninferior to responses after a single MenACWY-D dose. Seroresponse was defined as the proportion of subjects with a postvaccination hSBA titer ≥8 if the prevaccination (baseline) titer was <4, or at least a fourfold higher hSBA titer than baseline if the prevaccination titer was ≥4. Overall, the percentage of MenACWY-CRM and MenACWY-D participants aged 2 through 10 years with hSBA titers ≥8 was, respectively, 75% and 80% for serogroup A, 72% and 68% for serogroup C, 90% and 79% for serogroup W-135, and 77% and 60% for serogroup Y.4 Injection-site reactions within 7 days after vaccination included pain, erythema, and induration, and were common, with pain being most common. The most common systemic adverse effects were headache and irritability. Rates of adverse effects were similar to those seen after vaccination with MenACWY-D. Serious adverse events were reported in <1% of MenACWY-CRM recipients, and none were attributed to the vaccine.