H-Pylori is a well known cause of gastric cancer, gastric and peptic ulcers, and chronic gastritis in adults; we do not know, though, the role it plays in young children. Professor Miguel O'Ryan and his equipe have been studying this issue since decades trying to determine the rates of H-Pylori infection in Chilean population: one of the major conclusion is that adults that are infected were infected when children (acquiring the virus mostly between the second and the third year of life).
But the most interesting finding has demonstrated that infected children have differential expression of some relevant genes compared to non infected children (in particular cancer suppressor or cancer activator genes). What this means in time is matter of the studies currently going on, but it seems to suggest the opportunity in the future to prevent H-Pylori infection through vaccination.