13 September 2011

South Africa: Nation Gets Ready for Trial of Successful Thai Vaccine

Photo: Kate Holt/IRIN
Results of the RV144 Thai study gave hope that it is possible to find a vaccine to prevent HIV infection when it was found that the study vaccine had a 31% efficacy.

Two years ago, the AIDS community was electrified by news that a vaccine had partially protected people against HIV. Now this vaccine will be tested in South Africa.

This is according to scientists attending the International AIDS Vaccine conference, which opened yesterday (Monday) in Bangkok.

South Africa will be the first country outside of Thailand to have access to the only vaccine in 30 years to show any success against the virus that has killed millions of people, particularly in southern Africa.

The vaccine, known as RV144, protected 31 percent of the people who received it in a massive clinical trial in Thailand involving 16 400 people.

"The next step after the Thai trial was to rapidly test the vaccine in a country with a high incidence of HIV to see whether it would have the same results," said Wits University's Professor Glenda Gray.

"But there are a lot of challenges that have delayed the process since the results were announced two years ago," added Gray, who will lead the RV144 vaccine research when it starts in South Africa.

A key challenge has been to modify the Thai vaccine to fight the strain of HIV that is most common in South Africa.

Vaccines work by teaching a person's immune systems to recognise and destroy disease-causing pathogens (viruses and bacteria).

They usually contain a harmless part of the pathogen being targeted to prime the person's immune system to develop antibodies against it so that when it is attacked by the real pathogen, it already has the weapons to fight it.

The Thai trial combined two vaccines. The first aimed to prime people's immune systems to recognise the types of HIV most common in Thailand (sub-types E and B), and the other, injected later, aimed at boosting their immune systems to fight infection.

The "primer" vaccine now has to be modified to contain HIV sub-type C, which is most common in South Africa.

"But the company making the Thai vaccine closed down after the trial, so there was no one to make the product," said Gray. "[Pharmaceutical companies] Norvatis and Sanofi Pasteur are now working on making the vaccine, but first have to identify and insert parts of sub-type C into the primer vaccine."

Gray predicts that the trial will be ready to start in 2014, and involve around 8 000 people in up to 12 sites in South Africa.

The trial will be run by a collaboration of international and local groups, including the international HIV Vaccine Trials Network, the Gates Foundation and SA AIDS Vaccine Initiative (SAAVI), which is working with communities at various potential trial sites.

SAAVI has been working with communities at potential trial sites in Cape Town, Johannesburg, Pretoria, Durban, Klerksdorp and Mthatha.

SAAVI director Elise Levendal said she was very excited about the planned trial, adding that it was a credit to our country's scientists, government and community support for clinical trials that South Africa had been chosen.

"We work with communities to educate them and prepare them for vaccine research, and they keep asking us 'when is there going to be a vaccine trial'," said Levendal. "Now we can finally tell them something is going to happen."

Sanjay Gurunathan, representing a partnership of researchers, pharmaceutical companies and funders aimed at taking RV144 forward, said there had been some exciting post-trial analysis.

"In the first year of the trial, the vaccine protected 60 percent of people from HIV infection, but this effect waned over time to 31 percent," said Gurunathan.

"We think we might be able to increase this effect to 50 percent by boosting people's immune systems further."

Dr James Kublin, executive director of the HIV Vaccine Trials Network, said a vaccine that was 60 percent effective had the potential to have a "huge public health impact".

If such a vaccine reached 60 percent of the South African population, it could prevent over three million HIV infections in the country over 10 years, said Kublin.

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