BANGKOK (Thomson Reuters Foundation) - Researchers in Thailand will move ahead with another phase of an HIV vaccine study, building on a 2009 efficacy trial that provided the first evidence that a preventive HIV vaccine is possible.
The 2009 trial - known as RV144 - involved more than 16,000 volunteers in Thailand and found that the vaccine regimen tested reduced the risk of HIV infection by 31.2 percent at the end of the study, though the scientists noted that the efficacy rate at 12 months was significantly higher.
"The RV144 Thai HIV vaccine study results, announced in 2009, showed that a HIV vaccine is possible, and the protective effect at one year may have been as high as 60 percent,” Col. Jerome Kim, principal deputy of the U.S. Military HIV Research Program (MHRP) told Thomson Reuters Foundation by email after the AIDS Vaccine Efficacy Consortium (AVEC) Summit last week in Bangkok.
“Later scientific studies told us why the vaccine might have worked. This will allow us to tweak the vaccine and the schedule, which will hopefully increase the level of protection."
MHRP began a small clinical study, RV305, in April 2012 in Thailand to evaluate re-boosting in volunteers who participated in the RV144 study.
RV306, the immunogenicity study to begin this year, will compare additional vaccine boosts in 360 new volunteers and aims to determine “what types of immune responses the vaccine regimen generates, and which boost combinations generate the strongest response,” said Lisa Reilly, the MHRP’s communications director.
“It is not an efficacy study, so it does not need to be large… We are hoping to conduct an efficacy study with an improved vaccine boost/adjuvant in Thailand, but it will not start until 2016/17,” she said.
The RV306 study will be conducted at three sites: the Vaccine Trial Centre at Mahidol University and the Royal Thai Army Armed Forces Research Institute of Medical Sciences (AFRIMS), both in Bangkok, and the Royal Institute for Health Sciences (RIHES) in Chiang Mai.
Scientists have long sought an AIDS vaccine, with several failed attempts, including a 2007 trial in which a Merck vaccine appeared to make people more vulnerable to infection, not less.
Since the findings from the 2009 trial in Thailand, discoveries have pointed to even more powerful vaccines using HIV-fighting antibodies.
As many as 34 million people are infected with HIV worldwide. With 2.7 million new infections in 2010 alone, experts say a vaccine is still the best hope for eradicating AIDS.