In December 2023 the PrEPVacc HIV prevention study announced that vaccinations in the study have stopped due to “little or no chance” that the trial will demonstrate vaccine efficacy in preventing HIV acquisition. PrEPVacc reports that the leadership team have responded to the recommendation of the independent data monitoring committee that vaccinations should stop but that the oral PrEP component of the study should “continue to completion”. Follow-up for all participants will continue for data collection, HIV testing, and referral for ongoing care for six months after the final vaccine injection for participants or until the end of the oral PrEP trial.
PrEPVacc
PrEPVacc is a “three trials in one” approach that is led by African researchers “with support from European scientists”. The goal is to test two HIV vaccine combinations to assess if either can prevent infection in populations that are at risk of acquiring HIV. Around 1,500 volunteers in East and Southern Africa were enrolled.
Participants received injections of a combination of a DNA vaccine with a protein-based vaccine (AIDSVAX), a regimen combining DNA, MVA, and a protein-based vaccine (CN54gp140), or a placebo. While the vaccinations were underway the trial also tested a new oral pre-exposure prophylaxis (PrEP) drug formulation to see if it is as effective as drugs that are already approved.
The recent statement reflects that “despite the delays experienced due to the COVID-19 pandemic”, all participants but 10 had passed the time point for the third set of vaccinations by 2nd October 2023, with 1,016 having received all four vaccinations. Almost all participants elected to receive oral PrEP. However, after a scheduled interim review on 9th November, which considered data collected up to 2nd October, vaccinations were stopped immediately.
HIV: high hurdles
“The stopping of further vaccinations in PrEPVacc underlines how challenging it is to develop an effective HIV vaccine.”
The trial results will be shared with the public after the completion of study visits and analysis in the second half of 2024. PrEPVacc’s Trial Director, Dr Eugene Ruzagira, announced the news at the International Conference on AIDS and STIs in Africa (ICASA) 2023.
“The scientific hurdles are high, but I have equally high hopes that an HIV vaccine will be developed one day. Every day, all around the world, important research like PrEPVacc is moving us forward, and participants are willing to step forward with us and make a difference to the health of their communities.”
Dr Ruzagira reflected that the study built “very good relations” with participants and communities through the “principles and techniques” of Good Participatory Practice.
“As we move forward towards a new era of HIV prevention studies and vaccine efficacy trials, the lessons Good Participatory Practice have never been more important to apply.”
Professor Pontiano Kaleebu is PrEPVacc’s Chief Investigator and emphasised that the development of a preventative HIV vaccine is a “critical goal for Africa”, which 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. We must also look to a new generation of leaders.”
Professor Kaleebu commended participants and collaborators on their contributions to the “largest HIV vaccine efficacy trial to run in East Africa”. Professor Jonathan Weber is from Imperial College London in the UK, sponsor of the trial, and agreed on the importance of thanking and crediting the participants, who have made “a tremendous ongoing commitment to this study”.
“Our participants’ willingness to continue this study with us is heroic and greatly appreciated by the research community.”
Reflecting that “we do clinical trials because we don’t know the answer”, Professor Weber reckons that the interim result “puts this generation of putative HIV vaccines to bed”.
“It has been a tremendous achievement.”
The trial is not over
Professor Sheena McCormack, Project Lead based in the UK, offered the reminder that the trial is “three studies in one, and the PrEP part is continuing”.
“We hope that we will have valuable insights from the quantitative and qualitative findings to guide the use of oral PrEP beyond the trial.”
Olivia Nakanwagi of the Community Advisory Board concluded the statement with a positive reflection that the trial has tried “new ways to bring the community’s voice into decision-making”.
“I’m proud to represent my community among the study leaders, scientists, and staff at my site and guide them in engaging well with that community.”
This last comment is particularly relevant considering the recent call from UNAIDS: “let communities lead”. If you haven’t yet read the report, you can access it through the article here. If this trial has put “to bed” a generation of vaccines, what does the future of HIV vaccine efforts hold?
