AIDS Vaccine Still Out Of Reach
More than 30 years into the AIDS epidemic, the silver bullet against HIV still looks depressingly out of reach. As scientists, activists and health officials prepare for the International AIDS Society’s biennial meeting set to open in Mexico City this Sunday, hopes for progress toward a vaccine have crumbled amid disappointing scientific results and scrapped clinical trials.
Across Africa, where 25 million people are infected with HIV and new infections continue to outpace treatment, researchers and community leaders say the hunt must go on - but concede the setbacks have been demoralizing. “We cannot treat our way out of this epidemic — that is clear. We still need a vaccine,” said Fred Sawe, the medical director of the U.S. Military HIV Research Program in Kericho, Kenya, picked as one of the sites for vaccine trials.
“The community is ready to do its part. It is the scientists who have failed. We have not figured out the right product, and we still don’t know what we want the product to do,” Sawe said. The gloom threatens to overshadow more positive AIDS news, including evidence that male circumcision may help prevent transmission of the fatal and incurable virus and theories that HIV drugs could protect high risk individuals from infection - a concept referred to as pre-exposure prophylaxis or PrEP.
The life-saving HIV drugs, known as antiretrovirals or ARVs, are reaching more of the millions of people across Africa who need them. That is thanks in part to the U.S. President’s Emergency Plan for HIV/AIDS Relief or PEPFAR program, which Congress reauthorized last month as part of a $48 billion, five-year package.
But while PEPFAR funds have helped to bring AIDS treatment to nearly 2 million people, another 2 million people died of AIDS-related causes last year and 2.7 million were newly infected with the virus.
“The best hope of combating the HIV/AIDS epidemic is biomedical preventive technology, and the best among these would still be a vaccine,” said Dr. Gavin Churchyard of South Africa’s Aurum Institute, a health research organization engaged in vaccine work. “On AIDS, the rest has failed so far.”
BAD NEWS AND NEW STRATEGIES
Bad news on the vaccine front came last year when U.S. and South African scientists halted large-scale clinical trials of a vaccine prototype developed by Merck and Co citing safety concerns.
Preliminary data from the U.S. trial, known as STEP, showed that Merck’s vaccine may have raised the risk of infection among certain men - those who were uncircumcised and had pre-existing immune responses to the common adenovirus used to carry bits of HIV genetic material in the vaccine.
The Merck results spurred a major shift among U.S. government researchers, who recently announced they were scrapping a second planned large-scale trial of a similar vaccine prototype and would now concentrate on smaller, focused studies aimed at teasing out more basic information about HIV.
One big clinical AIDS vaccine trial remains under way in Thailand, but many scientists say they do not expect it to yield major results. Otherwise, only a few small “proof-of-concept” trials are planned, leaving the product pipeline essentially empty.
“We are in an interesting and, some would say, difficult period,” Dr. Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, which oversees U.S. federal vaccine research spending, said in a recent interview. “The obvious empirical approaches have not worked.”
Vaccine advocates say few scientists had expected big breakthroughs with either of the vaccine prototypes, and that even disappointing studies can deliver important new clues on how HIV works and how best to fight it.
“There has been a sense … that every vaccine trial is do or die,” Dr. Seth Berkley, president of the International AIDS Vaccine Initiative, said in a telephone interview.
“Most people don’t understand that the product development process is rife with failures. The assumption is most candidates won’t work. We are just looking for any signal of hope,” Berkley said.
And many of the volunteers in the failed Merck trial say they would sign up again despite the disappointments thus far.
“We have to take chances. You can’t just stay and watch people die,” said Jabulani Zantsi, an unemployed 23-year old from Soweto who participated in the trial.
“We are depending on ARVS, but ARVs don’t stop HIV. They just give you a longer life. We have to take the chance on a vaccine because HIV is not ending. It is only increasing.”