Meningococcal C specific immune responses: immunity in an era of immunization with vaccine

Meningococcal serogroup C conjugate immunization was introduced in the Dutch national immunization schedule at the age of 14 months, together with a large catch-up campaign in 2002. After introduction of this MenC immunization, the incidence of MenC completely disappeared from the immunized population and a large reduction of disease was observed in the non-immunized population. Little information was present on the longevity of immunity following a single MenC immunization. In this PhD thesis the immunity of the Dutch population was assessed before and after introduction of the vaccine. The study reveals that a single immunization is beneficial over naturally induced immunity against MenC and reveals that the persistence of MenC-specific antibodies gradually increases in relation with the age at the time of immunization. Therefore, the main success of the MenC immunization programme is mainly due to the large herd effect that was introduced after the mass catch-up campaign. However, children that receive a single MenC immunization at the age of 14 months may be at risk when they enter the adolescent age and therefore an additional immunization may be necessary. Furthermore, studies on the transfer of maternal antibodies from mother to neonate were performed and the kinetics of antibody responses following primary or secondary MenC conjugate vaccination were studied.