Long-term persistence of protective antibodies in Dutch adolescents following a meningococcal serogroup C tetanus booster vaccination.

INTRODUCTION: Due to waning immunity, infant vaccination with meningococcal serogroup C conjugated (MenCC) vaccines is insufficient to maintain long-term individual protection. Adolescent booster vaccination is thought to offer direct protection against invasive meningococcal disease (IMD) but also to reduce meningococcal carriage and transmission and in this way establish herd protection in the population. Previously, we studied antibody levels after adolescent MenCC booster vaccination. In the present study, the adolescent vaccinees were revisited after three years to determine antibody persistence and to predict long-term protection.

METHODS: Meningococcal serogroup C tetanus toxoid conjugated (MenC-TT) vaccine was administered to 10-, 12- and 15-year old participants who had been primed nine years earlier with a single dose of MenC-TT vaccine. Blood samples were collected before, 1month, 1year and 3years after the adolescent booster vaccination. Functional antibody levels were measured with serum bactericidal assay using rabbit complement (rSBA). Meningococcal serogroup C polysaccharide and tetanus toxoid specific antibody levels were measured using fluorescent-bead-based multiplex immunoassay. Long-term protection was estimated using longitudinal multilevel antibody decay modeling.

RESULTS: Of the original 268 participants, 201 (75%) were revisited after 3years. All participants still had an rSBA titer above the protective threshold of ⩾8 and 98% ⩾128. The 15-year-olds showed the highest antibody titers. Using a bi-exponential decay model, the median time to fall below the protection threshold (rSBA titer <8) was 16.3years, 45.9years and around 270years following the booster for the 10-, 12- and 15-year-olds, respectively.

CONCLUSIONS: After a first steep decline in antibody levels in the first year after the booster, antibody levels slowly declined between one and three years post-booster. A routine MenC-TT booster vaccination for adolescents in the Netherlands will likely provide long-term individual protection and potentially reduce the risk of resurgence of MenC disease in the general population.