All participants will receive three injections in an upper arm muscle-one injection a month for three months-with a needle-less device called a Biojector 2000® (Registered Trademark). At the time of each injection, participants will be observed for at least 1 hour after immunization. At home, they will record their temperature and any symptoms they may experience, including any effects at the injection site, for at least 7 days, or as long as the symptoms remain. If symptoms occur, participants will report them immediately to the clinic staff and, if necessary, come to the clinic for an examination.