The initial attempt in Africa to assess the efficacy of two combined vaccines against HIV has been terminated as researchers determined that the intervention was ineffective.

The trial involved 1,500 participants aged 18 to 40 in Uganda, Tanzania, and South Africa. Conducted under African leadership, the trial commenced in December 2020 and was discontinued last month following an interim assessment of its advancement.

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Dr Eugene Ruzagira, trial director from the Uganda Virus Research Institute (UVRI) and assistant professor of epidemiology at the London School of Hygiene and Tropical Medicine, told UK’s The Guardian that an analysis of the data collected by an independent data-monitoring committee led them to conclude that there is "little or no chance of demonstrating that the vaccines we are testing are reducing the risk of acquiring HIV.”

Led by African researchers with support from European scientists, the trials tested two different combinations of HIV vaccines to see if either could prevent infection in populations particularly at risk of infection.

Prof Jonathan Weber, from Imperial College London, one of the trial’s sponsors, said:

"We do clinical trials because we don’t know the answer to questions. It was important to find out whether the combination vaccine regimens in PrEPVacc, developed over 20 years, should be ruled out or further developed for preventing HIV.”

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"While we await the final results and analysis of individual products, I believe that our interim result puts this generation of putative HIV vaccines to bed,” he added.

Previous trials in South Africa to test the only vaccine that had shown any success in protecting against HIV – the RV144 – developed in Thailand, was stopped in February 2020 after interim results found it was not working.

Prof. Pontiano Kaleebu, PrEPVacc’s chief investigator at UVRI, said developing an effective vaccine to prevent HIV infection was "a critical goal for Africa”.

He said: "It is a goal that must have even greater urgency now that no HIV vaccines are being trialled for efficacy anywhere in the world.

"We have come so far in our HIV-prevention journey, but we must look to a new generation of vaccine approaches and technology to take us forward again.”

About 39 million people worldwide are living with HIV, more than 25 million in sub-Saharan Africa.