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The only HIV vaccine in advanced trials has failed. Now what?

The only HIV vaccine in advanced trials has failed. Now what?

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The only HIV vaccine still being tested in late-stage clinical trials has proved ineffective, its maker said Wednesday, another disappointment in a field that has long failed.

Dozens of HIV vaccine candidates have been tested and discarded over the past few decades. The latest defeat sets vaccine progress back three to five years, experts said. Still, other options in early-stage trials may prove powerful against HIV.

The news is “disappointing, but it’s not the end of vaccine development efforts,” Dr. Anthony Fauci, who led the National Institute of Allergy and Infectious Diseases until December, said in an interview. “There are other strategic approaches.”

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An ongoing trial called PrEPVacc in Eastern and Southern Africa is evaluating a combination of experimental HIV vaccines and preventive drugs. Scientists have made progress in developing powerful antibodies that can neutralize the virus. And they are testing new vaccine technologies, including mRNA, against HIV.

Still, the loss of the latest candidate underscores the challenges of designing a vaccine for an adversary as cunning as HIV. Four decades after its discovery, the virus still infects about 1.5 million people each year and kills about 650,000.

For people in wealthier nations, HIV is not the death sentence it once was. Powerful drugs can suppress the virus in infected individuals. There are several options for preventing the infection: oral pills and injections given every two months are already approved in the United States, for example, and an injection that only needs to be given every six months is in late-stage trials.

But these drugs must be taken for the rest of a patient’s life and are often unavailable to those who need them most. A vaccine would be the ideal way to thwart the virus.

“The best way to prevent any infection, especially a viral infection, is a vaccine that is safe and effective,” Fauci said. “This is why the field continues to conduct very active research in this area.”

The now-ending trial, called Mosaico, began in 2019 and was led by Janssen Pharmaceuticals, part of Johnson & Johnson. It tested the vaccine in 3,900 cisgender men (those who have always identified as men) and transgender individuals who have sex with cisgender men and transgender individuals at more than 50 sites in nine countries in North America, South America and Europe.

The vaccine contained a mosaic of components designed to target several different subtypes of HIV present around the world. But the immune response it provokes against the virus does not include significant amounts of so-called neutralizing antibodies, which are thought to be the most powerful weapon against infection.

While the trial’s failure doesn’t mean the end of the mosaic approach, it signals that a successful vaccine must prompt the body to produce broadly neutralizing antibodies, Fauci said.

After reviewing early data from the trial, an independent data and safety monitoring board concluded that while the vaccine was safe, it did not prevent more HIV infections than a placebo. The board recommended that the company stop the process and inform the participants.

The result didn’t completely surprise experts, as a study of the same vaccine, called Imbokodo, was halted in 2021. That trial tested the vaccine in cisgender women in five sub-Saharan African countries.

The failure of the studies is particularly disappointing in part because they were funded by Johnson & Johnson, said Mitchell Warren, executive director of the HIV prevention organization AVAC.

“It’s not like many companies are getting involved in infectious disease vaccines, so to see this not come to market is a disappointment and a setback,” Warren said.

The news should prompt policymakers and activists to think about ways to make existing HIV prevention tools more widely available, he added: “It’s not that all hope is lost, but that we need to redirect our resources to have the greatest impact.”

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