The first trial in Africa of two combination vaccines to prevent HIV was stopped after researchers concluded that it did not work.
The pre-exposure prophylaxis vaccine (PrEPVacc) was tested on 1,500 people between the ages of 18 and 40 in Uganda, Tanzania and South Africa.
The African-led trial, which began in December 2020, was halted last month after an interim review of progress. The final results are expected to be announced at the end of 2024.
Dr. Eugene Ruzagira, trial director of the Uganda Virus Research Institute (UVRI) and assistant professor of epidemiology at the London School of Hygiene & Tropical Medicine, said: “Vaccinations to PrEPVacc trial participants have been stopped because an analysis of the data collected so far by our independent data monitoring committee led have. them to conclude that there is little or no chance of showing that the vaccines we are testing reduce the risk of contracting HIV.”
The PrEPVacc trials, led by African researchers with support from European scientists, tested two different combinations of HIV to see if either could prevent infection in populations particularly at risk of infection. The trials were funded with a €15m (£12.8m) grant from the EU European & Developing Countries Clinical Trials Partnership.
Prof Jonathan Weber, from Imperial College London, one of the trial’s sponsors, said: “We do clinical trials because we don’t know the answers to questions. It was important to find out whether the combination vaccine regimens in PrEPVacc, developed over 20 years, should be excluded or further developed to prevent HIV.
“While we await the final results and analysis of individual products, I believe our interim result puts this generation of putative HIV vaccines to bed,” he said.
Previous trials in South Africa testing the only vaccine that has shown any success in protecting against HIV – the RV144 – developed in Thailand was stopped in February 2020 after interim results found it did not work.
Prof Pontiano Kaleebu, PrEPVacc’s principal investigator at UVRI, said the development of an effective vaccine to prevent HIV infection was “a critical goal for Africa”.
He said: “This is a goal that should have even greater urgency now that no HIV vaccines are being tested for effectiveness anywhere in the world.
“We have come so far in our HIV prevention journey, but we need to look to a new generation of vaccine approaches and technology to take us forward again.”
Over 39 million people worldwide living with HIV, more than 25 million in sub-Saharan Africa.
Speaking at an AIDS conference in Zimbabwe on Wednesday, Ruzagira said he remains optimistic. “The scientific hurdles are high, but I am equally hopeful that an HIV vaccine will one day be developed,” he said.
The RV144 vaccine was tested in Thailand between 2003 and 2006, which after three years infection rates reduced by almost a third.
