The earliest Phase I clinical trial for a DNA vaccine was of an HIV-1 candidate tested in individuals infected by HIV-1, followed by studies in volunteers who were not infected by HIV-1 [40] . Other prophylactic and therapeutic DNA vaccine trials followed, including trials that tested DNA vaccines against cancer influenza, malaria, hepatitis B, and other HIV-1 candidates [24, 41, 42] . These trials demonstrated that the DNA vaccine platform is well tolerated and safe, as no adverse events were reported and all studies went to completion.