**8. Conclusion**

*H. pylori* is the most common infection in humans and has infected humans since 30,000 years ago. The prevalence of *H. pylori* infection is still high particularly in developing countries. The highest prevalence is reported in Africa, namely Nigeria*. H. pylori* infection causes a wide spectrum of diseases from chronic gastritis to gastric adenocarcinoma. The disease has high morbidity and mortality rates. The burden from diseases caused by *H. pylori* is also heavy. The transmission of *H. pylori* is via oral-oral or fecal-oral routes. Contamination of water sources for drinking is a significant mode of transmission. The transmission is closely related to socioeconomic status, hygiene, and sanitation. *H. pylori* infection activates both innate and adaptive immunity. In adaptive immunity, Th1 response is dominant compared to Th2. Despite activating the immune system, *H. pylori* eradication by immune response is ineffective. *H. pylori* has abilities to escape from the host's immune system. In the innate immune system, *H. pylori* can neutralize gastric acid via urease enzyme activity and autoimmune-induced parietal cell loss. *H. pylori* prevents phagocytosis and promotes apoptosis of macrophages. Its LPS is less immunogenic compared to other gram-negative bacteria. Chronic infection hampers dendritic cell ability and disturbs activation of the adaptive immune response. In the adaptive immune system, *H. pylori* inhibit lymphocyte proliferation, induces T cell apoptosis, promotes Th2 activity and suppresses Th1 activity via Lewis antigen, and promotes Treg expansion thus dampens inflammation. External factors, such as coinfection with helminths, support the activity of Th2 and hamper *H. pylori* eradication. Genetic rearrangement is induced by *H. pylori* or by the host itself. The rearrangement alters immune response and causes ineffective eradication of *H. pylori*. Multiple antibiotic resistance is observed in *H. pylori,* particularly against metronidazole, clarithromycin, and levofloxacin. This contributes to persistent *H. pylori* infection. Vaccination becomes promising alternative management for preventing infection. Additionally, the vaccine may also have a therapeutic effect. However, the development of a vaccine should pay attention to the immune escape mechanism of *H. pylori*. Public health intervention is still important to holistically manage the infection.
