In The Lancet Infectious Diseases, Glenda Gray and colleagues report long-term follow-up results of the HVTN 503 or Phambili (which means "moving forward" in the Xhosa language) phase 2b efficacy trial of the Merck adenovirus type 5 (Ad5)-vectored DNA vaccine encoding HIV-1 subtype B gag, poi, and nef proteins. Phambili recruited South African participants at high risk of heterosexually transmitted HIV infection (subtype C); however, vaccinations were stopped during the enrolment phase after release of the interim efficacy analysis of the HVTN 502 Step study, which was assessing the same vaccine in men who have sex with men at risk of HIV infection in the Americas, Caribbean, and Australia. Interim results of Step showed futility for protective efficacy, and excess HIV infections in the vaccine group, noted very early after enrolment and initiation of vaccination. Because of the early closure of enrolment in the Phambili study, just 801 (27%) of the planned 3000 participants were recruited.
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