Kinetics of Immune Responses to Nasal Challenge With Meningococcal Polysaccharide 1 Year After Serogroup-C Glycoconjugate Vaccination

Background. Recipients of serogroup-C glycoconjugate meningococcal vaccine (MCC) exhibit waning of serum bactericidal antibody (SBA) titers, but the rate of decline and the speed of their immunological memory in response to new meningococcal nasopharyngeal colonization are unknown. Methods. In a prospective challenge study, we measured persistence of SBA and anti—Neisseria meningitidis serogroup-C (MenC) immunoglobulin (Ig) G and IgA in adults aged 18-39, 28 days and 12 months after receiving MCC. Volunteers were then challenged intranasally with 50 μg MenC polysaccharide to mimic meningococcal colonization, and systemic and mucosal antibody responses were measured. Results. All subjects had protective SBA titers (≥8) 28 days after MCC vaccination, but 12.3% and 20.2% had unprotective (