Trial ‘PrEPVacc’ was testing two different vaccine regimens on about 1,500 volunteers in Uganda, Tanzania and South Africa
Photo: iStock A trial of a human immunodeficiency virus (HIV) vaccine in Africa has been stopped after preliminary data showed it was not effective in preventing infections, according to officials. The study, known as PrEPVacc, was led by African researchers with support from European scientists. They were testing two different vaccine regimens on about 1,500 volunteers in Uganda, Tanzania and South Africa.
While there are drugs that can reduce the risk of getting HIV and treatments that can control the virus or prevent people from developing acquired immunodeficiency syndrome (AIDS), the news is a big blow to efforts to find an effective vaccine against a virus that has so far claimed about 40 million lives globally.
About 39 million people worldwide are living with HIV, with more than 25 million in sub-Saharan Africa, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS) and World Health Organization (WHO).
The African-led trial, which began in December 2020, has been stopped a year earlier after an interim review of its progress showed very little or no impact at all in some cases. The final findings are expected to be released in late 2024.
After multiple other high-profile trials failed in the past, PrEPVacc researchers were optimistic and had described the latest study as the final trial for this decade. The scientists involved expressed both concern and determination in the face of the unexpected results, promising fresh attempts in the next decade.
Eugene Ruzagira, trial director from the Uganda Virus Research Institute (UVRI) and assistant professor of epidemiology at the London School of Hygiene & Tropical Medicine, regretted the inefficacy of the vaccines.
“Vaccinations to PrEPVacc trial participants were stopped because an analysis of the data collected so far by our independent data-monitoring committee has 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,” Ruzagira said in a press statement.
Although disappointed with the outcome, an optimistic Ruzagira said the results have prompted the researchers to take a step back and reassess their strategies to understand the challenge better.
The trials were funded with a £12.8 million grant from the European Union’s European and Developing Countries Clinical Trials Partnership. The research was led by African researchers with support from various European institutions, like Imperial College London.
Besides two different combinations of experimental HIV vaccines, the research was also testing a new form of oral pre-exposure prophylaxis (PrEP), a drug that reduces the risk of getting HIV. That part of the trial is ongoing and is seeking to find out if the new PrEP (a drug that reduces the risk of getting HIV) is as effective as existing PrEPs.
In a statement to the press, Jonathan Weber from Imperial College London, one of the trial’s sponsors, emphasised the importance of transparency in such situations.
“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. 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,” Weber said in a press statement.
While the initial results are not what they had hoped for, it is crucial to communicate openly about setbacks in scientific research, he added. Transparency is integral to scientific processes and allows scientists to learn and adapt their strategies for future endeavours, acknowledged Weber, but remained optimistic about the broader picture.
Vaccine development is inherently complex, and setbacks are unfortunately part of the process, the researcher said in a statement.
“Our commitment to finding an effective HIV vaccine remains unwavering. We will carefully analyse the data, collaborate with our partners, and refine our approach to continue the fight against HIV / AIDS,” Weber said.
The disappointing results in Uganda, Tanzania, and South Africa underscore the need for a more nuanced and region-specific approach to vaccine development, said PrEPVacc’s chief investigator at UVRI Pontiano Kaleebu.
“We are determined to unravel the intricacies of HIV transmission in these regions and develop strategies that align with the unique dynamics of the virus,” said Kaleebu.
The unexpected outcome has prompted a comprehensive review of the trial's methodology and the vaccine’s formulation. Researchers are collaborating to identify potential variables that might have influenced the results and are exploring avenues for adjustments.
While the setback is disheartening, it is not uncommon in the realm of vaccine development. The global scientific community recognises that the path to a successful HIV vaccine is fraught with challenges, and setbacks are integral to the learning process. The halted trial provides an opportunity for researchers to refine their understanding of HIV transmission in different populations and design more targeted interventions.
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