A total of 48 healthy adult volunteers aged 18 to 49 years will be recruited. The first 24 subjects will be randomized 3:1 to SynGEM® low dose level (140 μg F-protein/2mg BLPs) or placebo administered at Day 1 and Day 29 (Group 1). After completion of recruitment of Group 1, if no pausing rule is met until 7 days post prime in all Group 1 subjects, 24 additional subjects will be randomized 3:1 to SynGEM® high dose level (350 μg F-protein/2mg BLPs) or placebo administered at Day 1 and Day 29 (Group 2).