NIAID: More research required in HIV Vaccine trial
The HVTN 503 trial began February 2007 to assess an investigational HIV vaccine developed by Merck & Co. The vaccine was supposed to prevent HIV infection for high-risk populations, mainly heterosexual males and females.
The vaccine mixed three weakened adenoviruses acting as carriers for transporting HIV proteins, gag, pol and nef, into the body. The weakened adenoverius type 5 (Ad 5) used in the vaccine was a modified common cold virus to reduce symptoms.
The study was stopped earlier than planned in September as a precaution, since another study found vaccinated subjects to have higher risk of HIV infection. When the study ended, 801 participants had been tested, although obtaining 3,000 participants was the initial intention at five sites throughout South Africa.
Of the 801 participants, 400 received the vaccine, but only a small percentage received the full dose; 112 received one vaccination, 259 received two and 29 participants received the full dose of three vaccinations.
After 30 months, participants were checked for rates of infection. 100 participants were found to be HIV positive, 63 whom received the vaccine and 37 whom did not. The results of the study were inconclusive, due to the low percentage of people who received full doses of the vaccine.
Researchers concluded further research necessary to determine the true efficacy of the vaccine. The follow-up study will be led by Glenda Gray, protocol chair at MBBCH, who also led HVTN 503.