Persistence of bactericidal antibodies 4 years after a booster dose of quadrivalent meningococcal diphtheria toxoid conjugate vaccine (MenACWY-D).

One dose of quadrivalent meningococcal conjugate vaccine (MenACWY) was first recommended for US adolescents (ages 11-12 years) in 2005 to protect against invasive meningococcal disease (IMD). In 2010, after evidence emerged about waning protection within 5 years after MenACWY vaccination, the US Advisory Committee on Immunization Practices (ACIP) recommended a MenACWY booster at age 16 years. We used a serum bactericidal assay with human complement (hSBA) to evaluate antibody persistence after a MenACWY-D booster in a sample of 110 participants who received the booster 4 years earlier in a phase 2 study. High proportions (89.9-98.2%) of participants maintained hSBA titers (≥1:4) associated with protection against IMD; a majority (81.7-97.2%) also had hSBA titers ≥1:8, a more conservative threshold. These findings support ACIP recommendations regarding MenACWY booster vaccination, which are aimed at protecting adolescents and young adults throughout the period in which they are at increased risk of IMD.