An effective HIV vaccine may not be ready for another decade despite ongoing efforts by scientists around the world, AIDS Vaccine 2012 conference heard this week (9–12 September).
In 2009 a trial in Thailand, called RV144 and involving 16,000 volunteers demonstrated, for the first time, that a vaccine can protect against HIV infection in humans. The vaccine trial represented a milestone for HIV vaccine research: "until this point there was no proof of concept", Bill Snow, director of the Global HIV Vaccine Enterprise, told the conference held in Boston, United States.
Further evidence of the vaccine's effectiveness against HIV infection was published in Nature this week (10 September). Researchers examined the genetic sequences of HIV viruses in people who received the vaccine and those who received a placebo, and found the vaccine was most effective against HIV viruses with two specific genetic footprints.
"This was an independent confirmation of the efficacy of the vaccine," Morgane Rolland, who led the research and is based at the US Military HIV Research Program, told SciDev.Net.
But despite the vaccine's success, researchers are struggling to overcome research and manufacturing challenges, and say that the process of making it ready for roll-out is taking longer than expected.
Speaking at the Boston conference, Jerome Kim, who led the study in Thailand and is based at the US Military HIV Research Program, said: "We underestimated issues related to manufacturing [the vaccine product to be used in trials]". Changes were made to increase the scale of the trial and guarantee the safety of the volunteers, prolonging the process.
In addition, researchers were not prepared for going to the next phase. The company that produced the component of the vaccine booster was small, and initially lacked capacity for producing the vaccine on a larger scale.
"The main reason for the delays in [further stage] RV144 trials is that they were not well prepared for success; nobody was ready for doing a follow-up study," Snow told SciDev.Net.
Another reason for the delay was the decision to move later stage trials to South Africa, where the epidemic is severe. South Africa has more people living with HIV, estimated at 5.6 million, than any other country in the world, according to the Joint UN Programme on HIV/AIDS.
The trial in South Africa is expected to start next year, but scientists will need to adapt the vaccine for the particular HIV viruses circulating in the region.
"We have to be realistic on where the timeline will leave us; after three years of experience, we are less optimistic to have short-term results," said Kim. "There is so much diversity [of the HIV virus], that it will never be possible to have a universal vaccine."
Kim highlighted that a vaccine is unlikely to be ready before the next decade.
But Bruce Walker, a researcher at the Harvard University Center for AIDS Research and co-chair of the Boston conference, said "the HIV vaccine is a solvable problem, it is only an issue of human and funding resources".
Nature doi:10.1038/nature11519 (2012)