In a blow to hopes for an HIV vaccine, a major trial has been abandoned because the vaccine being tested offered no effective protection. An interim, independent study found more people who had taken the vaccine went on to acquire HIV than those being administered a placebo.
The so-called HVTN 702 study was being led by the US’s National Institute of Allergy and Infectious Diseases (NIAID).
Launched in 2016, it was the first HIV vaccine to enter this phase of testing in seven years. It recruited over 5,400 HIV-negative individuals aged 18-35 across 15 sites in South Africa.
The country has one of the highest incidences of HIV transmission in the world, with more than 50% of women aged 18-25 living with the virus.
The vaccine moved on to this phase of testing after showing modest levels of protection in an earlier trial in Thailand. Researchers believed that although it only offered modest protection, this was better than no vaccine whatsoever, and therefore worth proceeding to the next stage of trials.
For this phase, the vaccine was modified slightly to target those strains of HIV most common in South Africa.
The trial has now been halted. An independent data and safety monitoring board (DSMB) followed up participants at least 18 months after they’d been enrolled. It found that there had been 252 HIV infections — 129 among vaccine recipients and 123 among placebo recipients. The DSMB did not express any concern regarding participant safety.
“An HIV vaccine is essential to end the global pandemic, and we hoped this vaccine candidate would work. Regrettably, it does not,” NIAID Director Anthony S. Fauci, MD, said in a press statement.
“The people of South Africa have made history by answering this important scientific question. Sadly, we wish the answer was different,” HVTN 702 Protocol Chair Glenda Gray, MBBCH, FCPaed, said in the statement.
“We will continue to explore promising avenues for preventing HIV with other vaccines and tools, both in South Africa and around the world.”
In early December, Fauci was one of two leading HIV experts to express the hope that an HIV vaccine was in the pipeline. Besides the HVTN 702 study, two other vaccines are currently being trialed in humans: Imbokodo and Mosaico.
Trials of Imbokodo began in South Africa began in 2017. Mosaico, which is a similar form of product to Imbokodo, began last November.
Both use a ‘mosaic’ of immunogens to provoke an immune response to a variety of different strains of HIV. They require six injections over four separate sessions.
While both are being trialed in South Africa, Mosaico will also be trialed in 3,800 gay men and trans people at 57 sites in the US, Latin America, and Europe.