Although scientists hope that a vaccine will eventually offer the best protection against HIV infection, the complex biology of the virus has posed constant challenges and even a partially effective vaccine is still some years away.
A number of potential HIV vaccines have made it out of the laboratory, but clinical trials on humans are still only in the second of three phases. The primary goals in the current round of trials are to establish safety, dosage and their ability to trigger an immune response.
Thandi Nxamakele, 27, from Klerksdorp, a gold mining town in South Africa's North West Province, was one of 240 South Africans who took part in a phase II HIV vaccine trial conducted by the Aurum Institute for Health Research, an independent medical scientific organisation.
She described her participation in the trial, which is now coming to an end, as "a privilege". "Before, we were never given an opportunity like this, we thought people who took part [in trials] were people who've got qualifications, but then everybody is welcome to take part in this research," she told IRIN/PlusNews.
According to Samuel Rampho, a study coordinator at Aurum's research site in Klerksdorp, volunteers tend to view participation in vaccine trials as their contribution to the AIDS fight. "Most would say they're very tired of this pandemic. Even if they don't benefit directly, people behind them might, so they feel it's something good they're doing for their communities."
Rampho also estimated that about 80 percent of trial participants had seen people close to them battle with the virus.
Chuma Ludidi, 22, was motivated by the experience of watching her older sister suffer from AIDS-related illnesses while trying to keep her status a secret from their devoutly Christian mother. Ludidi heard about the vaccine trial when she came to Aurum's voluntary counselling and testing (VCT) clinic last year to find out what her own HIV status was.
"I wanted to join, but during the physical screening they found out I had anaemia," she said. After being treated for the condition, Ludidi volunteered for a new vaccine trial, which is recruiting 3,000 participants between the ages of 18 and 35 at five different sites in South Africa.
Volunteering for the trial, known as "Phambili" (going forward), meant making a four-year commitment to visit the clinic at regular intervals and, in the case of female volunteers, avoiding pregnancy.
Ludidi said she didn't hesitate. "I thought, if I volunteer it will motivate other youth to come here and know better about HIV and AIDS," she said.
The Phambili trial is being advertised at public health clinics, local non-governmental organisations (NGOs) and youth centres, with slogans like "AIDS will be stopped by South Africans like you!"
"Dude, are you mad?"
Prospective participants are invited to attend an information session, in which they learn how an HIV vaccine works, the potential risks and benefits of taking part, and what would be required of them. Before signing an informed consent form, potential recruits must be HIV negative, undergo a thorough health screening and receive extensive counselling.
According to Ludidi, it is not fear of side effects from the vaccine that has prevented many of her friends from joining the trial; it is the fear of learning their HIV status. "They say 'If I've got HIV, I don't want to know, I'd rather die with it'."
Thabo Bonaventure, 22, an engineering student from Klerksdorp who participated in the earlier trial, got a similar reaction from his friends. "They'd say, 'Me, test? Dude, are you mad!'" Some of Bonaventure's college friends even "mocked" him for taking part in the trial, telling him, "you're going to get AIDS".
Rampho said one of the main challenges in recruitment has been explaining that HIV vaccines do not work like traditional vaccines, in which a weak version of the virus is administered in order to trigger the body's immune response when it is exposed to the real disease.
Instead, the vaccine delivers harmless copies of three HIV genes made in the laboratory. "We had one case where the mother of a participant was convinced her son was being injected with the HI virus," Rampho recalled. "We have to explain it doesn't work like a flu vaccine."
Volunteers are given symptom logbooks to record any side effects they might experience after having a vaccine shot. Prof Gavin Churchyard, principal investigator at the Aurum Institute in Klerksdorp, pointed out that only one participant in the phase II trial had experienced an "adverse event" that may have been related to the vaccine.
Most participants volunteer for altruistic reasons, but several reported appreciating the initial health screening and the regular check-ups. "It's not easy to get a full health screening at the public clinic," said Loretta Jonathan, 43, who took part in the earlier trial. "I'd have to pay a lot of money because I don't have medical aid [health insurance]."
Reducing risky behaviour
In line with ethical requirements, vaccine trial participants receive regular risk-reduction counselling, HIV testing, male and female condoms, and treatment for sexually transmitted infections.
Trial results are dependant on the fact that, despite all these measures, not all participants will use condoms all the time, but Churchyard said trial participants tended to reduce risky behaviour.
Several participants IRIN/PlusNews spoke to confirmed that their involvement in the trial had improved their knowledge of HIV and AIDS, and had influenced their behaviour.
"When you're at this age, maybe you don't care, you just sleep with this person and forget about HIV, but being in the study has made me more aware of those things," said Nxamakele.
Both Nxamakele and Ludidi viewed their participation in the trial as going beyond simply receiving the vaccines. Ludidi has persuaded several friends and family members to make use of Aurum's VCT services, while Nxamakele recently joined the organisation as a full-time trial recruiter. Jonathan has distributed HIV/AIDS pamphlets at local taverns on her own initiative.