Effective antimicrobial therapies have been developed to treat Helicobacter pylori that, with proper compliance, are more than 85% successful. Individual and population-based problems with pharmaceutical treatment, however, support a role for vaccination in the control of H. pylori infection. Current therapies require the patient to ingest multiple agents several times a day for at least 1 week. 77 Treatment can be accompanied by nausea, diarrhea, abdominal pain, and pseudomembranous colitis. 5,73 These adverse effects contribute to patient noncompliance and reduce the efficacy of the therapy. Additionally, these therapies are prohibitively expensive in developing nations where H. pylori infection is endemic with rates of infection as high as 80% to 90%. Widespread treatment of H. pylori could also result in the development of antibiotic resistant strains that have already been observed in patients treated with triple therapy in whom infection was not cured. 52,66 Additionally, antibiotic cure does not result in protective resistance to subsequent reinfection with H. pylori. It has been reported that successfully treated patients can become reinfected by accidental endoscopic transmission. 66 Finally, pharmaceutical therapies do not address the particular need of those nonsymptomatic individuals who might go on to develop gastric adenocarcinoma caused in part by H. pylori infection. 16 Despite the fact that individuals chronically infected with H. pylori mount a robust humoral immune response, several laboratories have demonstrated the efficacy of prophylactic and therapeutic immunization to prevent or cure H. pylori infection (see later discussion). Childhood vaccination could, in theory, provide an inexpensive and convenient solution to prevent adult gastritis and peptic ulcer disease and reduce the incidence of gastric cancer later in life.