Evaluation of serogroup C and ACWY meningococcal vaccine programs: projected impact on disease burden according to a stochastic two-strain dynamic model

Objective Advisory committees in Canada and the United States have updated recommendations for quadrivalent meningococcal conjugate vaccines against serogroups A, C, W135, and Y. Our objective was to evaluate optimally effective meningococcal vaccination policies using a stochastic dynamic model. Canada was used as an example. Methods Our stochastic dynamic model of Neisseria meningitidis (Nm) transmission in an age-structured population assumed partial cross-immunity among two aggregated serogroup categories: ‘AWY’ containing A, W135, and Y; and ‘Other’ containing B, C, and ungroupable types. We compared the impact of monovalent C versus quadrivalent ACWY vaccination on Nm carriage and invasive meningococcal disease (IMD). Our model was parameterized with Canadian epidemiological and demographic data and employed probabilistic sensitivity analysis. Results Routine infant immunization at 12 months and boosting at 15 years with a quadrivalent vaccine is projected to have the largest impact on total IMD incidence: a 74% reduction over 40 years. Routine infant immunization with a monovalent vaccine at 12 months only has much less impact and also generates strain replacement appearing after approximately ten years of continuous use. Conclusions Immunizing infants at 12 months and boosting adolescents at 15 years with an ACWY vaccine is predicted to be most effective at reducing IMD incidence.