Prior to receiving the vaccine, the chosen vaccine administration site on the back or thigh was disinfected and exfoliated. A skin patch was applied to the site, and the vaccine solution was placed on the skin underneath the patch with a needleless syringe. Participants were allowed to remove the skin patch 3 hours post vaccination. For the first and second vaccinations, participants were required to remain at the clinic for 3 hours post-vaccination so study staff can assess for side effects. If no side effects occurred after the first two vaccinations, participants were required to stay at the clinic for only 30 minutes after receiving later vaccinations.