Background & aims: Helicobacter pylori is most likely acquired in childhood, but the incidence of infection has not been determined prospectively by using an appropriate noninvasive test. The aim of this study was to determine the age-specific incidence of Helicobacter pylori infection in children and the risk factors for infection.
Methods: Three hundred twenty-seven healthy index children between 24 and 48 months of age were enrolled over 15 months. At baseline, the Helicobacter pylori infection status of each index child and his or her older siblings and parents was assessed by using the carbon 13-urea breath test. All noninfected index children were then followed up with an annual carbon 13-urea breath test for 4 years to determine whether they became infected with Helicobacter pylori and, if so, the age at first infection. Information on potential risk factors was collected at baseline and each subsequent visit.
Results: At baseline assessment, 28 of 327 (8.6%) index children were infected with Helicobacter pylori. The mean age of the 28 infected children was 32.78 months (SD, 5.14 months). Over the next 4 years, 279 index children not infected at baseline contributed 970 person-years of follow-up to the study. During this time, 20 children became infected with Helicobacter pylori. The rate of infection per 100 person-years of follow-up was highest in the 2-3-year age group (5.05 per 100 person-years of follow-up (95% confidence interval, 1.64-11.78) and declined progressively as children aged. Only 1 child became infected after 5 years of age. Having an infected mother, an infected older sibling, and delayed weaning from a feeding bottle (ie, after 24 months of age) were all risk factors for infection.
Conclusions: Children who become infected with Helicobacter pylori are infected at a very young age, and the risk of infection declines rapidly after 5 years of age. These findings have important implications for studies on the mode of transmission of infection.