Fourteen volunteers are entered at one of two dose levels of multivalent candidate vaccine. At each dose level, 12 volunteers receive vaccine and two receive placebo. At least eight volunteers at the low dose level must be monitored for 2 weeks before subsequent volunteers are entered at the high dose. Intramuscular injections are given on days 0, 28, and 168, and patients are followed for a minimum of 48 weeks after the initial immunization. Approximately 13 clinical visits are required.