Conjugate vaccines for preventing meningococcal C meningitis and septicaemia

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Abstract
Meningococcal polysaccharide (MPLS) vaccines protect against Serogroup C disease, but do not produce an immune response in infants less than two years of age. This limitation can be overcome by linking C polysaccharide to carrier proteins ('conjugating'), to create meningococcal serogroup C conjugate (MCC) vaccines. In the absence of trial data, the immune response to vaccination has been considered to be a reasonable surrogate for vaccine protection. To assess the immunogenicity, safety and efficacy of MCC vaccines for preventing meningitis and septicaemia. We searched the Cochrane Central Register Controlled Trials (CENTRAL) (The Cochrane Library 2005, issue 3); MEDLINE (1966 to September, Week 1 2005); and EMBASE (1990 to June 2005) and references of studies. Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in humans comparing MCC vaccines against a control vaccine or none. In the absence of any trials on vaccine efficacy, population‐based observational studies about effectiveness were included. Two authors independently screened the results of the literature searches, selected eligible studies, extracted the data and evaluated the quality of them. The studies showed that MCC vaccine was highly immunogenic in infants after two and three doses, in toddlers after one and two doses and in older age groups after one dose. In general higher titres were generated after MCC than after MPLS vaccines. Immunological hypo‐responsiveness seen after repeated doses of MPLS vaccine may be overcome with MCC. Observational studies have documented a significant decline in meningococcal C disease in countries where MCC vaccines have been widely used. The timing of the vaccinations schedules, the specific conjugate used, and the vaccines given concomitantly or combined, may be important. The MCC vaccine appears to be safe, immunogenic and able to induce immunological memory in all age groups. Observational studies strongly suggest that MCC is clinically effective.