Breakthrough as vaccine cuts HIV infection risk

AN experimental vaccine has prevented infection with the Aids virus for the first time, a breakthrough in the fight against the deadly illness.

The World Health Organisation and the UN agency UNAids said yesterday the results “instilled new hope” in the field of HIV vaccine research.

The vaccine cut the risk of becoming infected with HIV by more than 31% in the world’s largest Aids trial of more than 16,000 volunteers in Thailand.

Even though the benefit is modest, “it’s the first evidence that we could have a safe and effective preventive vaccine”, said colonel Jerome Kim who helped lead the study for the US Army, which sponsored it with the National Institute of Allergy and Infectious Diseases.

The institute’s director, Dr Anthony Fauci, warned this was “not the end of the road”, but said he was pleased by the outcome.

“It gives me cautious optimism about the possibility of improving this result” and developing a more effective Aids vaccine, he said. “It is something that we can do.”

The Thailand Ministry of Public Health conducted the study, which used strains of HIV common in Thailand. Whether such a vaccine would work against other strains in the US, Africa or elsewhere in the world is unknown.

Even a marginally helpful vaccine could have a big impact. Every day, 7,500 people worldwide are newly infected with HIV; two million died of Aids in 2007.

“Today marks a historic milestone,” said Mitchell Warren, executive director of the Aids Vaccine Advocacy Coalition, an international group that has worked toward developing a vaccine. “There is little doubt that this finding will energise and redirect the Aids vaccine field,” he said.

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

They are ALVAC, from Sanofi Pasteur, the vaccine division of French drugmaker Sanofi-Aventis; and AidsVAX, originally developed by VaxGen and now held by Global Solutions for Infectious Diseases, a non-profit founded by some former VaxGen employees.

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. The vaccines are not made from whole virus – dead or alive – and cannot cause HIV.

Neither vaccine in the study prevented HIV infection when tested individually in earlier trials, and dozens of scientists had called the new one futile when it began in 2003.

“I really didn’t have high hopes at all that we would see a positive result,” Mr Fauci confessed.

The results proved the sceptics wrong.

“The combination is stronger than each of the individual members,” said Colonel Kim, a physician who manages the army’s HIV vaccine programme.

The study tested the combo in HIV-negative Thai men and women aged 18 to 30 at average risk of becoming infected. Half received four “priming” doses of ALVAC and two “boost” doses of AidsVAX over six months. The others received dummy shots. No one knew who got what until the study ended.

Thanad Yomha, a 33-year-old electrician from south-eastern Thailand, said he did not expect anything in return for volunteering for the project.

“I did this for others,” Thanad said. “It’s for the next generation.”

All were given condoms, counselling and treatment for any sexually transmitted infections, and were tested every six months for HIV. Any who became infected were given free treatment with antiviral medicines.

Participants were followed for three years after vaccination ended.

The results: New infections occurred in 51 of the 8,197 people given vaccine and in 74 of the 8,198 who received dummy shots. That worked out to a 31% lower risk of infection for the vaccine group. Two of the infected participants who received the placebo died.

The vaccine had no effect on levels of HIV in the blood for those who did become infected. That had been another goal of the study – seeing whether the vaccine could limit damage to the immune system and help keep infected people from developing full-blown Aids.

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