/ 22 September 2007

Promising HIV vaccine trial halted in SA

A major HIV vaccine trial in South Africa was brought to a halt on Friday after interim results from a sister trial in the United States and Australia suggested it failed to prevent HIV infection.

The news came as a major blow to Aids researchers as the vaccine had been billed as the world’s most promising Aids-vaccine candidate.

The South African trial was at the most advanced clinical stage of any HIV vaccine trial on the African continent.

”It’s been a very bad day for us. We all feel terribly despondent at the news,” Dr Glenda Gray, chief investigator in the South African trial of the Merck MRKAd5 vaccine based at Chris Hani Baragwanath Hospital in Soweto said in an interview.

Seven hundred people had enrolled in the trial, code-named Phambili, that began at five sites across South Africa in February this year.

The trial sought to test the efficacy of the vaccine in fighting the C subtype of the HI virus found in Africa after preliminary results from trials in other parts of the world had suggested it had some success in fighting the B subtype strain.

But the trial was paused on Friday after interim results from a trial carried out in regions with the B subtype, including the US and Australia, showed it probably did not protect against HIV infection.

The organisers of the South African trial will take a month to examine the data from the sister trial before deciding whether to continue with the Phambili trial in a modified form or suspend it, Gray said.

The researcher stressed that the safety of the volunteers in the trial was never in jeopardy as the vaccine’s safety had been borne out in earlier testing.

”We do know it’s safe and that it won’t cause HIV, but we don’t know if it protects against HIV infection,” she said.

Preliminary results from the Phambili trial had shown a good immune response, but it now looks as if a good immune response might not necessarily lead to HIV protection, Gray explained.

South African researchers will examine whether factors such as gender and means of contracting HIV may have influenced the results of the sister trial. More than 90% of the volunteers in that trial were male. The South African trial is more evenly split between men and women.

Two other HIV vaccine trials are under way in South Africa, one aimed at prevent the transmission of HIV, another aimed at treating its symptoms.

South Africa has the largest number of HIV-positive people worldwide. About 5,4-million South Africans, or one in nine, are infected. — Sapa-dpa