Part I will evaluate the safety, tolerability, and immunogenicity of 1 or 2 doses of the HA-F A/Sing vaccine in a dose-escalation design. In Group 1, five subjects will receive a low dose of the HA-F A/Sing vaccine via needle and syringe on Day 0. If this low dose is assessed as safe and well tolerated, enrollment will begin for Group 2. In Group 2, five subjects will receive the