African-led HIV-PrEP vaccine combination commences human trials

UGANDA— PrEPVacc study, funded by the European & Developing Countries Clinical Trials Partnership (EDCTP2) programme, has commenced human trails of the HIV-PrEP combination vaccine in four sites in East and Southern Africa.

The trial involves a combination efficacy study in Africa of two DNA-MVA- or DNA- Env protein HIV-1 vaccine regimens with pre-exposure prophylaxis i.e., the PrEPVacc study.

The PrEPVacc study trials will take place in Masaka in Uganda, Mbeya & Dar-es-Salaam in Tanzania, and Durban in South Africa.

PrEPVacc is led by African researchers from Entebbe in Uganda, at the Medical Research Council (MRC) of the Uganda Virus Research Institute, and London School of Hygiene and Tropical Medicine (LSHTM) Uganda Research Unit.

PrEPVacc has been an African-led, European-supported HIV prevention study that has been running in East and Southern Africa from 2018 to 2024.

PrEPVacc is a public-private partnership and EDCTP awarded a US$16.4 million grant for the study and all the institutional partners are providing co-funding through staff salaries.

The study is scheduled to disseminate its findings by December 2024.

By the end of their contribution over 17 months after the first vaccine injection, they will have made at least 15 study visits.

For the first time, it is combining the evaluation of experimental HIV vaccines and pre-exposure prophylaxis (PrEP) at the same time.

The PrEPVacc team announced that enrolment began in December 2020 and concluded in March 2023, due to disruptions during the Covid-19 pandemic.

The enrolment targets have been achieved in all the sites with 1,512 participants having been enrolled out of the total 2,215 potential participants that were screened for enrolment.

Moreover, of the participants, 1,504 have started vaccinations, 623 were still receiving vaccines, and 671 had completed their fourth vaccination (of four scheduled).

“Participants are healthy adults aged 18-40 years who have voluntarily given full informed consent to take part in the PrEPVacc study, which has been approved by their site’s Research Ethics Committee,” said the team in a news release.

One-of-a-kind vaccine combo

Led by African researchers, PrEPVacc is the first HIV vaccine efficacy trial to be conducted in East Africa and the only HIV vaccine efficacy trial being conducted in the world at present.

Its findings will inform scientists as to whether developing either of the two different combination vaccine regimens for preventing HIV is worthwhile or not, even with the smaller sample size.

If efficacy is shown, and the combination vaccine is safe, the result will need to be confirmed through further trials.

PrEPVacc will also provide insights into PrEP adherence when needed for prevention and whether the new form of PrEP (Descovy) is as acceptable, safe, and effective as the available oral standard PrEP (Truvada) among women.

PrEPVacc is testing two different ways to prevent HIV, at the same time, which include HIV vaccine regimens against a placebo (saline), and a new form of oral pre-exposure prophylaxis (PrEP) against the existing standard for PrEP.

Participants received injections of either one regimen combining DNA with a protein-based vaccine, or a regimen combining DNA, MVA, and a protein-based vaccine, or a placebo (saline).

They were all also offered study PrEP as Descovy or Truvada through to two weeks after the third injection, and thereafter as locally sourced PrEP equivalent to Truvada.

PrEPVacc’s Trial Director Dr. Eugene Ruzagira said, “We have worked hard and skilfully through very challenging periods during the Covid-19 pandemic in order to successfully and safely reach this point.”

Dr. Ruzagira added that they had already shared the outcomes of our social science work with relevant stakeholders, and we’re committed to sharing news about results that emerge from PrEPVacc with the participants and their communities first.

Challenges of successfully recruiting and enrolling into a clinical trial during the Covid-19 pandemic, and supply challenges with the MVA vaccine, PrEPVacc’s Investigators proposed a change to the randomization of enrolled participants.

Behind the Scenes: organizing a large-scale vaccine trial in Africa

The PrEPVacc trial was preceded by a preparedness study known as the “Registration Cohort” which gave research teams a better understanding of the community and HIV infection rates in the context of the PrEP roll-out.

During the registration, sites developed a Community Advisory Board or Community Working Group whose members are locals who partner with the researchers and bring the concerns and interests of the community and study participants to the researchers.

The study is supported by 15 partner organizations, six from Africa, six from Europe, and three from the U.S.

The organizations are the MRC/UVRI and LSHTM Uganda Research Unit in Uganda, Muhimbili University of Health and Allied Sciences, Tanzania, and the National Institute for Medical Research – Mbeya Medical Research Centre in Tanzania both from East Africa.

From South Africa are the HIV and Other Infectious Diseases Research Unit, South African MRC, South Africa, and the Africa Health Research Institute.

Partners drawn from Europe are the Imperial College London, UK, Medical Research Council Clinical Trials Unit at University College London, UK, Centre Hospitalier Universitaire Vaudois, Switzerland, Karolinska Instituet, Sweden, Medical Center of the University of Munich (LMU), Germany, EuroVacc Foundation, and IAVI.

While from the U.S. is Gilead Inc., Global Solutions for Infectious Diseases, and the East Virginia Medical School, Conrad, U.S.

There is currently no vaccine available to prevent HIV infection and scientists are working to develop a vaccine to prevent infection by the HIV virus.

The development of a safe, effective, preventive HIV vaccine remains key to realizing a durable end to the HIV/Aids pandemic.

Researchers across the globe are pursuing numerous strategies to develop next-generation vaccine candidates.

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