Fig. 5
The booster vaccination phase study design. Group B received the Zagreb regimen as the primary vaccination, followed by one dose of the booster vaccination. Group C received the Zagreb regimen as the primary vaccination, followed by two doses of the booster vaccination. Group E received the Essen regimen as the primary vaccination, followed by one dose of the booster vaccination. Group F received the Essen regimen as the primary vaccination, followed by two doses of the booster vaccination. The booster vaccination was conducted 6 months after the primary vaccination. The day on which blood samples were collected from individuals due to receive the first booster was defined as Day 0 in the booster vaccination phase. Blood samples were collected at 12 months after the primary vaccination, which was approximately 6 months after the booster was given; this timepoint was defined as Month 6 in the booster vaccination phase.
