Objective: To determine the incidence of H. pylori recurrent infection after successful eradication in 4-year follow-up study, and to evaluate the influencing factors for re-infection.
Material and Method: Thirty-seven patients (age range 20-74 years; average 49.06 + 14.03 years) were recruited of which 64.9% were females. The H. pylori infection was proved to be successfully eradicated in all patients. Annually, urea breath test (UBT) was assessed to determine H. pylori status after eradication. Age, sex, eating habit, water drinking, number of children, and treatment regimens against H. pylori were recorded. A breath test was also performed on the patient’s spouse.
Results: The H. pylori recurrence occurred in 5/37 (13.51%) of patients observed. There were two patients in the first year, one patient each in the second, third, and fourth year. The cumulative re-infection rate was 5.41% at 1-year, 8.11% at 2-year, 10.81% at 3-year, and 13.51% at 4-year. H. pylori infection of spouse was also frequent (80%). Even if the spouse was infected, 88.89% of patients will remain uninfected after 4-years of H. pylori eradication. No influencing factor for infection recurrence was detected.
Conclusions: The risk of re-infection after H. pylori eradication was low in Thai patients after 4-year follow up. Annual re-infection rate was 3.38%. No dependent factors were associated with a recurrence.

Keywords: H. pylori, Recurrent, Thailand