Table 3. Other outcomes measures description.

Outcome measure	Measure description
Prevalence of H. pylori persistent infection in adolescents in Colina, Temuco and Aysén.	Two initial UBT tests will be performed separated by 1 month; a third UBT test will be obtained if there is a discordance in results of the first two tests.
Effect of treatment on frequency of clarithromycin resistance comparing those subjects who would not eradicate with non-treated individuals.	Stool evaluation for presence of Clarithromycin resistance genes will be performed in stool samples obtained before eradication (30 in each group), and within 6 months after the positive UBT sample indicating non-eradication in conjunction with testing of a similar number of non-treated UBT positive subjects (20 in each group, including 10 treated and non-eradicated subjects).
Overall reinfection rates in adolescents with successful eradication after treatment.	UBT test performed 1 month after the last day of treatment to confirm eradication, and then 6 months after treatment and, subsequently, every 6 months to evaluate reinfection up to 24 months post-treatment.
Change in the percentage of adolescents, which have ‘gastric disease’ according to gastroenterologist examination from posteradication to postreinfection.	Clinical evaluations by a gastroenterologist or trained physician, blinded to the subject’s treatment arm, will be conducted after successful eradication (2–4 months post-treatment), and subsequently, at 9–12 months and 18–24 months post-treatment to assess specific GI signs and symptoms and their changes in relation to reinfection during this follow-up period.
Change in blood levels of biomarkers indicative of gastric damage postreinfection as compared with postsuccessful eradication.	A blood sample will be collected within 6 months after the positive UBT sample indicating reinfection. Biomarkers will be analysed as described in primary endpoints.
Change in gut microbiome alpha-diversity index postreinfection as compared with postsuccessful eradication.	A stool sample will be collected within 6 months after the positive UBT sample indicating reinfection. Gut microbiome analysis will be performed according to what is described in secondary endpoints.
Change in faecal Escherichia coli and Enterococcus AMR rates postreinfection as compared with postsuccessful eradication.	A stool sample will be collected within 6 months after the positive UBT sample indicating reinfection. AMR will be analysed as described in secondary endpoints.

AMRantimicrobial resistanceH. pyloriHelicobacter pyloriUBTurea breath test