Figure 1. Course of H pylori infection in vaccinated volunteers. A breath test was used to monitor the course of infection in experimentally challenged volunteers over time. (A, B) [13C]urea breath test (UBT) results of 4 Ty21a control (□) and 9 Ty21a(pUreA/B) (▪) vaccinated volunteers in the first study. (C, D) UBT results of control (□), Ty21a(pUreA/B) (▪) and Ty21a(pHP0231) (•) vaccinated volunteers in the second study. Values correspond to mean (SD) UBT results of vaccine groups repeatedly tested at the indicated times postchallenge infection. (B) and (D) UBT results over time of individual volunteers in study 1 and 2, respectively, who although initially testing positive after challenge, tested repeatedly negative (threshold UBT values DoB <1.5; stippled line) after week 3. ‘Ch.’ and arrow denote time of challenge infection, ‘Treatment’ and arrow mark the start time of antibiotic eradication.DoB, delta over baseline.