Fifty healthy Ugandan volunteers, considered at low risk for HIV infection, have begun receiving injections of a prototype HIV vaccine designed to target the strain of virus indigenous to East Africa. This part of the trial is expected to last two years, according to researcher Dr. Pontiano Kaleebu, and it will attempt to determine whether the vaccine is safe and generates immunity. The vaccine used in the study contains no HIV and cannot cause infection, but it is the only one in human trials so far that is designed to target HIV subtype A, the prevalent strain of the virus in Uganda and other East African nations. Uganda was the epicenter of the AIDS epidemic in the early 1980s, but studies have shown that the nation has been successful in stalling the spread of HIV using aggressive abstinence and safe sex educational programs. Phase two of the trial will involve a larger number of healthy, low-risk volunteers, while the third and final phase will pit the vaccine against a large high-risk volunteer population.