Issues surrounding standardization of meningococcal group W135 serology

Persistence of the immune response after MenACWY-CRM vaccination and response to a booster dose, in adolescents, children and infants

Persistence of bactericidal antibodies following vaccination is extremely important for protection against invasive meningococcal disease, given the epidemiology and rapid progression of meningococcal infection. We present an analysis of antibody persistence and booster response to MenACWY-CRM, in adolescents, children and infants, from 7 clinical studies. Immunogenicity was assessed using the serum bactericidal assay with both human and rabbit complement. Post-vaccination hSBA titers were high, with an age- and serogroup-specific decline in titers up to 1 y and stable levels up to 5 y The waning of hSBA titers over time was more pronounced among infants and toddlers and the greatest for serogroup A. However, rSBA titers against serogroup A were consistently higher and showed little decline over time, suggesting that protection against this serogroup may be sustained. A single booster dose of MenACWY-CRM administered at 3 to 5 y induced a robust immune response in all age groups.

Seroprevalence of serum bactericidal antibodies against group W135 and Y meningococci in England in 2009

Serological surveillance has been used in the United Kingdom to inform vaccine policy for several infections, including those with group C meningococci. Meningococcal conjugate vaccines, containing capsular groups A, W135, and Y in addition to C, are now available, but their use in the United Kingdom is restricted to at-risk groups and travelers to areas of endemicity. The aim of this study was to establish a baseline for natural immunity for groups W135 and Y. Serum samples collected in 2009 from individuals of all ages were obtained from the Health Protection Agency Seroepidemiology Unit, which collects residual sera from participating laboratories across the country. Serum bactericidal antibody (SBA) activity against two reference strains, representing groups Y (strain M03 241125) and W135 (strain M01 240070), was determined with 1,191 sera using a standardized complement-mediated SBA assay, with complement derived from baby rabbits (rSBA). The age-specific geometric mean titers (GMTs) and percentages of individuals with rSBA titers of ≥ 8 were calculated, together with 95% confidence intervals (CI). Overall, 18.4% and 19.6% had rSBA titers of ≥ 8 for groups W135 and Y, respectively. Antibody prevalence varied by age. In general, rSBA titers were low for younger children, with serum samples from 7% and 13% of children under 5 years achieving titers of ≥ 8 against groups W135 and Y, respectively. GMTs peaked for 20- to 24-year-olds for group W135 (GMT, 7.1; 95% CI, 4.7, 10.9) and for 30- to 44-year-olds for group Y (GMT, 8.6; 95% CI, 5.9, 12.7). Unlike seroprevalence against group B meningococci, there was not an obvious peak in SBA titers in samples from teenagers. Natural immunity against group W135 and Y meningococci in England appears to be low.

Quadrivalent meningococcal ACYW-135 glycoconjugate vaccine for broader protection from infancy

Invasive meningococcal disease is a global public-health concern, with infants and adolescents bearing the majority of the disease burden. Vaccination is the most rational strategy to prevent meningococcal disease. Control of serogroup C disease has largely been achieved by the introduction of glycoconjugate meningococcal C vaccines, initially in the UK in 1999, and subsequently in several other countries. The recent licensure of a quadrivalent glycoconjugate vaccine against serogroups A, C, Y and W-135 in the USA and Canada has broadened protection against Neisseria meningitidis in 2-55 year olds. The investigational quadrivalent meningococcal serogroup A, C, Y and W-135 glycoconjugate vaccine (MenACYW-CRM197), which is immunogenic from infancy, has the potential to extend protection to the most vulnerable age group. This article discusses this novel quadrivalent vaccine formulation and its potential to control invasive disease caused by N. meningitidis serogroups A, C, Y and W-135.