Recombinant blood group antigen-binding adhesin (BabA) can be used in a composition to raise humoral immune response i.e. antibodies, that target conserved structural epitopes in the fucosylated blood group antigen Lewis b (Leb) antigen binding domain in the blood group antigen-binding adhesin (BabA). Such broadly Leb-blocking antibodies can reduce the gastric mucosal attachment of Helicobacter pylori (H. pylori) to human gastric mucosa. This approach can be used for preventing and/or alleviating gastric disease in a subject diagnosed with H. pylori infection, said gastric disease chosen from gastroesophageal reflux disease, chronic active gastritis, peptic ulcer diseases, gastric ulcer disease, gastric cancer gastritis and gastric cancer, in particular gastric cancer. It also becomes possible to identify subjects that carry BabA positive H. pylori infections and subjects that are at risk of developing severe gastric disease, such as peptic ulcer diseases, gastric ulcer disease, gastritis with metaplasia and gastric cancer.