This is a Phase 1/2, single-center, randomized, open-label, non-controlled trial. Approximately 30 healthy volunteers, male or female, aged 20-65, will be randomized to one of the following three groups.

Group A: Vaccination twice at 2-week intervals (n = 10) Group B: Vaccination twice at 4-week intervals (n = 10) Group C: Vaccination 3 times at 2-week intervals (n = 10)