In a setback for the global effort to develop an effective HIV vaccine, the results of the PrEPVacc clinical trial have shown that two experimental vaccine regimens failed to reduce new HIV infections among the study population in Eastern and Southern Africa.
The PrEPVacc trial, which ran from 2020 to 2024 across sites in Uganda, Tanzania, and South Africa, tested two different vaccine combinations against a placebo.
According to a PrEPVacc results that were announced yesterday during the AIDS conference in Munich Germany, the data showed more infections in the vaccine arms compared to the placebo arm, though the researchers said the statistical confidence intervals were too wide to draw definitive conclusions.
Notably, the trial also found an unusually low rate of HIV infection in the placebo group, which could not be explained by differences in condom use or PrEP (pre-exposure prophylaxis) uptake. The PrEPVacc team plans to conduct further analyses to better understand the immunological factors behind the results.
“The PrEPVacc vaccine trial results, announced today at AIDS 2024 in Munich, Germany, report more infections in the two vaccine arms than in the placebo arms, but the researchers say they cannot draw a definitive conclusion about what this means because the statistical ‘confidence intervals’ for the comparison are so wide, indicating a high degree of uncertainty,” read the report.
The news comes as the world grapples with the continued HIV/AIDS epidemic. UNAIDS estimates that in 2022, a total of 10.7 million people were living with HIV and 244,000 adults and children were newly diagnosed across South Africa, Tanzania, and Uganda – the countries where the PrEPVacc trial was conducted.
At the time of the trial’s completion, PrEPVacc was the only ongoing HIV vaccine efficacy study worldwide, underscoring the critical need for further research and innovation in this field. The failure of the two vaccine regimens tested in this trial represents a major setback in the global quest to develop an effective HIV vaccine.
