Aids vaccine on trial in South Africa
Cape Town - The only vaccine to have shown efficacy in protecting against HIV infection is to be tested in South Africa, prompting excitement among scientists and raising hopes the HIV pandemic might finally be defeated.
Thousands of South Africans will take part in the clinical trial, known as HVTN 702, in November, that will be testing a modified version of a vaccine that showed a modest protection against HIV seven years ago.
In 2009 the RV144 vaccine trial showed a 31 percent efficacy against HIV infection in a study conducted in Thailand.
This week it was announced at the HIV Vaccine Trial Network Conference in Washington, DC that a smaller trial that tested safety and immunogenicity of the modified vaccine had been successful.
These results paved the way for the three-year trial, which would enrol more than 5 000 HIV-negative adults, to commence in South Africa. Men and women between 18 and 35 who are at risk of HIV infection will go through the trial, which will test whether the latest vaccine is safe, tolerable and effective in preventing HIV infection.
While the follow-up study was expected to be similar to the original Thai trial, it had since been modified to match the South African strain of HIV, known as subtype C.
If it proves at least 50 percent successful in preventing infection, the vaccine will be licensed.
In 2009, the pox protein-based vaccine, which was tested on more than 16 000 people in Thailand, provided the first evidence in humans that a safe and effective vaccine was possible. It remains the only HIV vaccine to have shown some efficacy.
While the Thailand study has provided some hope, scientists are puzzled by the evasive nature of HIV and the complexity of finding vaccines, with some seeming to lead to an increased risk of infection rather than protecting against it.
In South Africa, the study will be carried out by the pox protein public private-partnership (P5) consortium comprised of major international organisations. These include the US Military HIV Research Programme, the Medical Research Council of South Africa (MRC), the Bill and Melinda Gates Foundation and the HIV Vaccine Trials Network.
The trial will be led by MRC president and research professor of paediatrics at Wits University Glenda Gray. It will test a vaccine regimen that consists of two experimental vaccines: a canarypox-based vaccine called Alvac-HIV, and a bivalent gp 120 protein subunit vaccine with an adjuvant that enhances the body's immune response to a vaccine.
Gray said the latest vaccine would tell scientists “whether the initial success observed in the HVTN 100 (smaller trial) will bear fruit in the form of a safe and effective HIV vaccine”.
Professor Linda-Gail Bekker, deputy director of the UCT-based Desmond Tutu HIV Foundation, said a prophylactic vaccine was one of the most effective ways to gain control on an epidemic.
“Being able to protect people against infection so that they can get a vaccine shot and then not have to worry again about taking pills, makes prevention manageable on a large scale. Even a partially effective vaccine has been shown in modelling studies to have significant impact on incidence, and therefore overall better control on the epidemic.”
She said scientists would also learn a lot about correlates and biomarkers - data and information that was critical for “getting us closer to a fully preventive vaccine and ultimate epidemic control”.
South Africa was among the countries worst-affected by HIV, according to Professor Francois Venter, head of the Southern African HIV Clinicians Society. “We still have lots of new infections, over 1 000 day. We desperately need new options.”