Abstract
The Nobel Prize in Physiology or Medicine in 2005 has been awarded to B. Marshall and R. Warren for their discovery that peptic ulcer disease is caused by an infection with Helicobacter pylori. This infection, which affects about half of the world's population and is already extremely prevalent in adolescents in developing countries, starts as an asymptomatic gastritis which, under certain conditions, is followed by gastric or duodenal ulcer disease. No proven benefit has yet been found by treating H. pylori-infected children with gastritis unless they have a peptic ulcer. Vaccination against H. pylori infection during early childhood is considered a means of preventing peptic ulcer disease and also possibly adenocarcinoma.