title: Modeling Long-term Vaccination Strategies With MenAfriVac in the African Meningitis Belt.
abstract: BACKGROUND
  The introduction of MenAfriVac in campaigns targeting people aged 1-29 years across the African meningitis belt has successfully reduced meningitis incidence and carriage due to Neisseria meningitidis group A (MenA). It is important to consider how best to sustain population protection in the long term.
  
  
  METHODS
  We created a mathematical model of MenA transmission and disease to investigate the potential impact of a range of immunization strategies. The model is age structured; includes classes of susceptible, carrier, ill, and immune people (who may be vaccinated or unvaccinated); and incorporates seasonal transmission and a stochastic forcing term that models between year variation in rates of transmission. Model parameters were primarily derived from African sources. The model can describe the typical annual incidence of meningitis in the prevaccine era, with irregular epidemics of varying size. Parameter and structural uncertainty were explored in sensitivity analyses.
  
  
  RESULTS
  Following MenAfriVac introduction at high uptake, the model predicts excellent short-term disease control. With no subsequent immunization, strong resurgences in disease incidence were predicted after approximately 15 years (assuming 10 years' average vaccine protection). Routine immunization at 9 months of age resulted in lower average annual incidence than regular mass campaigns of 1- to 4-year-olds, provided coverage was above approximately 60%. The strategy with the lowest overall average annual incidence and longest time to resurgence was achieved using a combination strategy of introduction into the Expanded Programme on Immunization at 9 months, 5 years after the initial mass campaigns, with a catch-up targeting unvaccinated 1- to 4-year-olds.
  
  
  CONCLUSIONS
  These results can be used to inform policy recommendations for long-term vaccination strategies with MenAfriVac.
authors.affiliation: Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, United Kingdom.
authors.forename: Andromachi
authors.initials: A
authors.lastname: Karachaliou
authors.affiliation: Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, United Kingdom.
authors.forename: Andrew J K
authors.initials: AJ
authors.lastname: Conlan
authors.affiliation: Meningitis Vaccine Project, PATH, Ferney-Voltaire, France Meningitis Vaccine Project, Department of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Preziosi
authors.affiliation: Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, United Kingdom.
authors.forename: Caroline L
authors.initials: CL
authors.lastname: Trotter
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000453:epidemiology; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008585:Meningitis, Meningococcal / Q000453:epidemiology* / Q000517:prevention & control* / Q000635:transmission; D022401:Meningococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D008875:Middle Aged; D008962:Models, Theoretical; D012621:Seasons; D014611:Vaccination / Q000379:methods* / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: C573970:MenAfriVac; D022401:Meningococcal Vaccines
keywords: Africa; mathematical modeling; meningitis; vaccine