Healthy children, 6-12 years old, will undergo screening for H. pylori infection by measuring anti-H. pylori and CagA IgG antibodies in the serum. The status of H. pylori infection will be confirmed using breath test (UBT). Children will be classified as i) H. pylori negative, if they test negative on UBT ii) H. pylori positive- CagA negative, if they test positive on UBT, but lack serum CagA IgG antibodies iii) H. pylori positive- CagA positive, if they are positive for H. pylori on UBT and CagA IgG antibodies.

Healthy children, 6-12 years old, will undergo screening for H. pylori infection by measuring anti-H. pylori and CagA IgG antibodies in the serum. The status of H. pylori infection will be confirmed using breath test (UBT). Children will be classified as i) H. pylori negative, if they test negative on UBT ii) H. pylori positive- CagA negative, if they test positive on UBT, but lack serum CagA IgG antibodies iii) H. pylori positive- CagA positive, if they are positive for H. pylori on UBT and CagA IgG antibodies.

The means of the differences in height for age Z score between baseline and follow-up visits

The means of the differences in weight for age Z score between baseline and follow-up visits

The means of the differences in body mass index for age Z score between baseline and follow-up visits

The means of the differences in iron biomarkers (hemoglobin, ferritin, iron) between baseline and follow-up visits

Changes in full-Scale IQ scores and-sub-scores on WISC test between baseline and 24-months follow-up visit: will be defined as the means of the differences of these scores.