Observer-blind, partially randomized, multi-center dose-escalation Phase I study in healthy adults below 40 years of age.

180 subjects will be enrolled in 6 treatment groups (different doses; different formulation: with/without adjuvant); vaccinations will be given I.M.(intramuscular) into the deltoid region on Days 0, 28 and 56. Study participants will be followed up until one year after first vaccination.

Booster Extension:

Subjects in the 48µg and 90µg Treatment groups who received a complete Primary immunization schedule will be included into a Booster Extension 13 months after the first immunization.