Modelling the impact of 4CMenB and MenACWY meningococcal combined vaccination strategies including potential 4CMenB cross-protection: An application to England.

Invasive meningococcal disease (IMD), an uncommon but severe disease, affects mainly infants, young children and adolescents. Meningococcal B (4CMenB) and ACWY (MenACWY) vaccines targeting IMD-causing serogroups B and A, C, W and Y, respectively are available for these mostly-affected age-groups. The objective was to assess the impact of 4CMenB and/or MenACWY vaccination strategies on IMD in England, considering MenACWY carriage protection and potential cross-protection of 4CMenB against non-B serogroups. A novel dynamic transmission model was developed, accounting for vaccine characteristics, with separate variables for meningococcal carriage and IMD for three groups: B; ACWY; and 'Other' mostly non-pathogenic serogroups. A dynamic force of infection is assumed for each group. The model analysis uses data from England before 2015 (when 4CMenB and MenACWY were introduced), and accounts for existing MenC vaccination impact. Compared with no vaccination, the smallest decrease in IMD cases is observed for MenACWY strategies (toddler and/or adolescent). 4CMenB (infant or infant/adolescent), alone or with MenACWY, always results in the most rapid and steep decline in IMD cases. Combined strategies with adolescent 4CMenB result in the largest decrease in IMD cases, whereas adding MenACWY for toddlers has a minor impact. With potential 4CMenB cross-protection, 4CMenB infant strategy has a notable impact on reduction of MenW and MenY IMD cases in strategies where MenACWY toddler and/or adolescent vaccination is absent. This novel model allows for analysis of combined 4CMenB and MenACWY strategies including potential 4CMenB cross-protection. In settings comparable to England, a comprehensive meningococcal vaccination programme should include infant 4CMenB as essential building block. Decisions to include MenACWY toddler programmes should consider herd effects of MenACWY adolescent programmes and 4CMenB potential cross-protection effects. Extending 4CMenB infant and MenACWY adolescent programmes with a 4CMenB adolescent programme allows for the largest overall reduction in IMD cases.