Participants are given one of three doses of the vaccine, depending on when they enter the study. The first 25 people enrolled receive a dose of 90 micrograms (mcg). If this dose is well tolerated, the next 25 people receive 120 mcg, and if this dose is also well tolerated, the last 25 people receive 180 mcg. Vaccination consists of either two shots (one in the muscle of each arm) or one shot in the buttock on four occasions. Subjects are vaccinated on four occasions, each 4 weeks apart. On the day of each vaccination, subjects provide a blood sample to evaluate blood counts, chemistries, and antibody levels, and to test for HIV, hepatitis B and C, syphilis, and antibody against avian flu. For 7 days after each vaccination, subjects keep a diary card to record any symptoms, such as pain, fever, muscle aches, or others. At the end of the 7 days, they are contacted by study staff to report the symptoms.