Meningococcal serogroup C serum and salivary antibody responses to meningococcal quadrivalent conjugate vaccine in Saudi Arabian adolescents previously vaccinated with bivalent and quadrivalent meningococcal polysaccharide vaccine

Following repeated polysaccharide vaccination, reduced immune responses have been reported, but there are limited data on the mucosal response of meningococcal polysaccharide vaccine (PSV) or meningococcal conjugate vaccination. Saudi Arabian adolescents (aged 16-19 years) who had previously been vaccinated with ≥1 dose of bivalent meningococcal polysaccharide vaccine and 1 dose of quadrivalent meningococcal polysaccharide (MPSV4) were enrolled in a controlled, randomised, and modified observer-blind study (collectively termed the PSV-exposed group). The PSV-exposed group was randomised to receive either quadrivalent meningococcal conjugate vaccine (MCV4) (PSV-exposed/MCV4 group) or MPSV4 (PSV-exposed/MPSV4 group), and a PSV-naïve group received MCV4. Serum and saliva samples were collected pre-vaccination and 28 days post-vaccination. Serum serogroup-specific A, C, W and Y IgG were quantified as were salivary serogroup-specific C IgG and IgA together with total salivary IgG and IgA. For each serogroup, the post-vaccination serum geometric mean concentrations (GMCs) were significantly higher in the PSV-naïve and the PSV-exposed/MCV4 group than in the PSV-exposed/PSV4 group. For serogroup C, serum serogroup-specific IgG for the PSV-naïve group was significantly higher than both the PSV exposed groups. Higher levels of salivary serogroup C-specific IgG were found in the PSV-naïve group than those who had received two doses of polysaccharide but no significant differences were noted with regards to serogroup-specific IgA.