A primary Helicobacter pylori infection does not protect against reinfection in children after eradication therapy

Background. Helicobacter pylori infection is one of the most common chronic infections in the world, and is acquired mainly during childhood. It is not clear to which extent a primary infection protects the child from reinfection. Our aim was to determine the possible protection conferred by a primary infection against H. pylori reinfection in children. Methods. A follow-up study with 120 children distributed in two cohorts; the first included 80 children without previous H. pylori infection (primo-infection cohort); the second included 40 infected children successfully eradicated (reinfection cohort). Cohorts were monitored during 2 years with urea-breath-test (UBT) at 3, 6, 9, 12, 18 and 24 months for the acquisition of H. pylori infection. We compared the rate of reinfection in eradicated children with the rate of infection in children without previous infection. H. pylori infection during the follow-up was analyzed and compared between cohorts using chi(2) and survival curves. A questionnaire was performed for the evaluation of possible risk factors for infection in both cohorts. Results. No significant differences in rates of primo-infection or reinfection were found; 17 (21.2%) primo-infections and 10 (25%) reinfections were documented. Most of the primo-infections (14/17) occurred in the first year of follow-up. In contrast, reinfection episodes occurred more frequently during the second year (6/10). In both cohorts, most infections were transient. Risk factors were similar for both, primo and reinfection cohorts. Conclusion. A primary infection does not protect from reinfection in the population of children studied.