Antibody persistence after serogroup C meningococcal conjugate vaccine in children with sickle cell disease.

Background: A decline of protective antibody titers after MCC vaccine has been demonstrated in healthy children, this may be an issue of concern for risk groups. The aim of this study was to evaluate the persistence of bactericidal antibodies after MCC vaccine in sickle cell disease (SCD) patients. The type of vaccine used and booster response were also analyzed.

Methods: SCD patients (n=141) previously immunized with MCC vaccines had blood drawn 2-8 years after the last priming dose. They were distributed according to age at primary immunization into groups: <2 years and 2-13 years and evaluated by years since vaccination (2-3, 4-5 and 6-8). Serum bactericidal antibodies with baby rabbit complement (rSBA) and serogroup C-specific IgG concentrations were measured. The correlate of protection was rSBA titer ⩾8. Subjects with rSBA <8 received a booster dose and antibody levels re-evaluated after 4-6 weeks.

Results: For children primed under 2years of age rSBA titer ⩾8 was demonstrated in 53.3%, 21.7% and 35.0%, 2-3, 4-5, 6-8years, respectively, after vaccination, compared with 70.0%, 45.0% and 53.5%, respectively, for individuals primed at ages 2-13years. rSBA median titers and IgG median levels were higher in the older group. Six to eight years after vaccination the percentage of patients with rSBA titers ⩾8 was significantly higher in the group primed with MCC-TT (78.5%) compared with those primed with MCC-CRM197 [Menjugate® (33.3%) or Meningitec® (35.7%)] (p=0.033). After a booster, 98% achieved rSBA titer ⩾8.

Conclusion: Immunity to meningococcal serogroup C in SCD children declines rapidly after vaccination and is dependent on the age at priming. Booster doses are needed to maintain protection in SCD patients. Persistence of antibodies seems to be longer in individuals primed with MCC-TT vaccine comparing to those immunized with MCC-CRM197.