title: Quantifying the population impact of a prophylactic Helicobacter pylori vaccine.
abstract: BACKGROUND
  Helicobacter pylori vaccines, which have been suggested as promising interventions to control infection, are under development. We sought to quantify the potential population impact of a prophylactic H. pylori vaccine.
  
  
  METHODS
  We developed a mathematical model that compartmentalized the population according to age, infection status and clinical state. A proportion of individuals was assumed to acquire infection and develop gastritis, duodenal ulcer (DU), chronic atrophic gastritis and gastric cancer (GC). We first simulated the model without vaccine intervention, to obtain estimates of H. pylori prevalence, and GC and DU incidences based on intrinsic dynamics. We then incorporated a prophylactic vaccine (80% efficacy, lifetime protection, 80% coverage) targeting all infants. We tested vaccination programs over unlimited as well as limited time spans. Analyses were performed for the US, Japan and a prototypical developing country.
  
  
  RESULTS
  In the US, our model predicted a decrease in H. pylori prevalence from 12.0% in 2010 to 4.2% in 2100 without intervention. With 10 years of vaccination beginning in 2010, prevalence would decrease to 0.7% by year 2100. In the same period, incidence of H. pylori-attributable GC would decrease from 4.5 to 0.4 per 100,000 with vaccine (compared to 1.3 per 100,000 without vaccine). Incidence of H. pylori-attributable DU would decrease from 33.3 to 2.5 per 100,000 with vaccine (compared to 12.2 per 100,000 without vaccine). In Japan, incidence of H. pylori-attributable GC would decrease from 17.6 to 1.0 per 100,000 after 10 years of vaccination (compared to 3.0 per 100,000 without vaccine). In a prototypical developing country, after 10 years of vaccination, H. pylori-attributable GC would decrease from 31.8 to 22.5 per 100,000 by 2090, returning to the original level by mid-2100s. Under continuous vaccination, it would decrease to 5.8 per 100,000 by 2100.
  
  
  CONCLUSIONS
  In the US and Japan, a 10-year vaccination program would confer almost the same reduction in H. pylori and associated diseases as a vaccination effort that extends beyond 10 years. In developing countries, a continuous vaccination effort would be required to eliminate the pathogen and its associated diseases.
authors.affiliation: Department of Management Science and Engineering, Stanford University, Stanford, CA 94305, USA. marcia.rupnow@stanfordalumni.org
authors.forename: M F
authors.initials: MF
authors.lastname: Rupnow
authors.forename: R D
authors.initials: RD
authors.lastname: Shachter
authors.forename: D K
authors.initials: DK
authors.lastname: Owens
authors.forename: J
authors.initials: J
authors.lastname: Parsonnet
mesh_terms: D003906:Developing Countries; D004381:Duodenal Ulcer / Q000517:prevention & control; D005756:Gastritis / Q000517:prevention & control; D016481:Helicobacter Infections / Q000276:immunology / Q000517:prevention & control*; D016480:Helicobacter pylori / Q000276:immunology*; D006801:Humans; D007223:Infant; D007564:Japan; D008954:Models, Biological; D012680:Sensitivity and Specificity; D013274:Stomach Neoplasms / Q000517:prevention & control; D013997:Time Factors; D014481:United States; D014611:Vaccination / Q000379:methods