Gastric cancer remains a major challenge to public health on a global scale. H. pylori related cancer burden contributes to the largest proportion of cancer cases attributable to infections in Europe. Considering its absolute burden and persisting disparities, in addition to the substantial prevalence of H. pylori infection worldwide that is treatable, gastric cancer is a logical target for urgent action for prevention. Population-based H. pylori test-and-treat has therefore been proposed as a strategy for gastric cancer prevention. To fill the gaps in knowledge about gastric cancer prevention through H. pylori screening and eradication in younger adults, a study of a population-based H. pylori test-and-treat strategy in Ireland, Croatia, Latvia, Poland, Romania and Slovenia. Main goals of this study are to assess future program processes, feasibility, acceptability and effectiveness. In total of 6,800 adults aged 30-34 will be tested for H. pylori infection. They will be randomly selected to represent the chosen population and invited to participate in the study based on informed consent. Confirmed infections will be treated by available combined therapy in line with treatment guidelines and the success of eradication will be retested during a control check-up. Patients who will provide their consent to participate will undertake an interview about the risk factors in early childhood and their habits regarding alcohol consumption and use of tobacco. Compliance to testing and treatment, treatment results, adverse effects and reasons for dropping out will be additionally monitored. Gathered data will be analysed in alignment with our research questions. The investigators will disseminate reports and present the results to both the general public and the scientific community in order to foster future developments in gastric cancer prevention.