HIV breakthrough as scientists discover new vaccine to prevent infection

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HIV breakthrough as scientists discover new vaccine to prevent infection

First evidence of possible vaccine as US military-backed medical trial in Thailand cuts HIV infection rate by a third
Sarah Boseley, health editor, and Haroon Siddique guardian.co.uk, Thursday 24 September 2009 11.20 BST Article history

A microscopic image of the HIV virus.


A medical trial in Thailand has raised hopes of a major breakthrough in the fight against Aids after scientists said an experimental vaccine had reduced the risk of HIV infection by a third.

The world's largest HIV/Aids vaccine trial of more than 16,000 volunteers was the first in which infection has been prevented, according to the US army, which sponsored the trial with the National Institute of Allergy and Infectious Diseases.

A combination of two vaccines was tested on HIV-negative Thai men and women aged 18 to 30 at average risk of becoming infected. All the volunteers were given counselling and condoms to help them avoid HIV. Then half were randomly picked to receive the vaccine, while the other half got dummy shots. Until the trial ended, nobody knew who had been given the genuine vaccine and who had not.

A relatively small number of people became infected with HIV – 51 of the 8,197 people given the vaccine, and 74 of the 8,198 who received dummy shots – but the difference was statistically significant, which means scientists believe it could not have happened by chance. It worked out at a 31% lower risk of infection for the vaccine group.

Colonel Jerome Kim, who helped to lead the $105m (£64m) study for the US army, said it was "the first evidence that we could have a safe and effective preventive vaccine".

Recent failures had led many scientists to believe that such a vaccine might not be achievable. In 2007, the drug company Merck abandoned what had looked at the time like the most promising avenue of research after disappointing trial results. Today the National Institute's director, Dr Anthony Fauci, warned it was "not the end of the road", but said he was surprised and very pleased by the outcome.

"It gives me cautious optimism about the possibility of improving this result," he said. "This is something that we can do."

Every day, 7,000 people worldwide are newly infected with HIV; 2 million died of Aids in 2007, the UN agency Unaids estimates.

The Aids Vaccine Advocacy Coalition, an international group that has worked towards developing a vaccine, welcomed the results of the trial – the third major study since 1983, when HIV was identified as the cause of Aids – as "a historic milestone".

The executive director, Mitchell Warren, said: "There is little doubt that this finding will energise and redirect the Aids vaccine field."

Frances Gotch, professor of immunology at Imperial College London, said the results appeared to be statistically significant and may have been the effect of the two different vaccines working in tandem to more powerful effect.

"The fact that they have seen a response with people with such a low incidence of infection is impressive," Gotch, who is also the principal investigator for the International Aids Vaccine Initiative, told the Guardian.

"Of course it's not 100% of people [protected] but 31% could make an enormous difference in the world. I think this is something we can work with."

Thailand's ministry of public health conducted the study, which used strains of HIV common in Thailand.

Scientists stressed it was not known whether such a vaccine would work against other strains elsewhere in the world. The study was done in Thailand because US army scientists carried out pivotal research in that country when the Aids epidemic emerged there, isolating virus strains and providing genetic information on them to vaccine makers.

The study tested a two-vaccine combination in a "prime-boost" approach, where the first one primes the immune system to attack the HIV virus, and the second one strengthens the response.

Alvac uses canarypox, a bird virus, altered so it can't cause human disease, to ferry synthetic versions of three HIV genes into the body. AidsVax contains a genetically engineered version of a protein on HIV's surface.

It is unclear whether vaccine makers will seek to license the two-vaccine combination in Thailand. Before the trial began, the US Food and Drug Administration said other studies would be needed before the vaccine could be considered for US licensing. The full results of the trial will be presented at an international Aids vaccine conference in Paris in October.

The executive director of the Global HIV Vaccine Enterprise, an alliance of research bodies and funders like the Gates Foundation, said the results showed a vaccine was an achievable goal. "This is a historic day in the 26-year quest to develop an Aids vaccine," said Dr Alan Bernstein. "This trial is the first demonstration in humans that, with more research, it will be possible to develop a vaccine that is fully protective against HIV."

Deborah Jack, chief executive of the National Aids Trust in the UK, said a vaccine, by far the most effective way of tackling serious infectious diseases, was desperately needed. More work was needed, but the promising findings "justify the continuing investments and efforts of the international community, including the UK government, to develop a vaccine."

The Terrence Higgins Trust said it was treating the results with "cautious optimism".

"This is the first step on a very long road," said the policy manager, Vicky Sheard.

"There's a lot of research needed into how a vaccine can be rolled out, how costly it's going to be, whether it's going to be effective against different strains."

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HIV trial provides hope
Vaccine effective in a third of volunteers
Writer: APIRADEE TREERUTKUARKUL
Published: 25/09/2009 at 12:00 AM

Newspaper section: NewsA breakthrough in the world's largest and long-running HIV vaccine trial has given new hope in the battle against HIV/Aids.

The results of the trial carried out in Thailand released yesterday show the vaccine has 31.2% efficacy in preventing HIV/Aids infections.



Although its effectiveness did not reach the 50% efficacy rate needed to apply for a vaccine licence, and the vaccine, tested on over 16,000 volunteers in Chon Buri and Rayong, cannot lower the level of virus in the blood, the result was considered a success.

"The outcome represents a significant finding in HIV vaccine development because for the first time ever there is evidence that an Aids vaccine has preventive efficacy," Public Health Minister Witthaya Kaewparadai said.

"Although it is not high enough for use, the result will help future vaccine research and development."

No previous vaccine trials have shown evidence of success against the virus.

Jerome Kim, deputy director (science) of the US Military Research Programme, a partner in the project, hailed the results as a big step forward.

"Although the results were modest, this is a very important scientific advance and gives us hope that a globally effective vaccine may be possible in the future," Col Kim said.

Researchers would have to determine why the vaccine worked, he said.

Other project participants are the National Institute of Health and vaccine manufacturers Sanofi Pasteur and Global Solutions for Infectious Disease.

The Thai Phase III HIV vaccine clinical trial began in October 2003.

The so-called prime-boost test combines two vaccines - Alvac, which was created by France-based Sanofi Pasteur, and Aidsvax B/E, made by Global Solutions for Infectious Disease - to stimulate different immune response systems simultaneously.

Each volunteer was given a vaccine or a placebo over a one-year period and checked after at least three and a half years.

It was controversial at the beginning mainly because of the previous failure of the Aidsvax component. Initially, the US$105 million (3.5 billion baht) project also faced a shortfall in volunteers.

Principal investigator Supachai Rerks-ngarm said infected volunteers developed roughly the same amount of virus in their blood whether they were given the vaccine or the placebo.

At the start of the trial, none of the volunteers was infected. Half received the vaccine and the rest were given a placebo. Of the placebo recipients 74 of 8,198 became infected compared with 51 of 8,197 who received the vaccine.

Two volunteers also died.

The vaccine was tested on volunteers - all HIV negative men and women aged from 18 to 30 - at average risk of infection starting in October 2003.

Dr Supachai said it would take some time before a new Aids vaccine trial would start as scientists still had to analyse what particular response was effective in the clinical trial held in Thailand.

Scientists also have to report findings on volunteers and decide if a long-term project monitoring volunteers should be carried out since the efficacy did not match the researchers' goal.

Mitchell Warren, executive director of the New York-based Global Advocacy for HIV Prevention, said talks about the effect of the vaccine were needed.

US ambassador to Thailand Eric John hoped the result would help Aids vaccine research.

"This trial will be recognised. The conclusion has brought us one step closer to Aids vaccine development."