Trials to determine if a HIV PrEP vaccination is effective have started in earnest in four sites in East and southern Africa

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

According to the research team, 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.

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 dated June 9.

Enrollment began in December 2020 and concluded in March 2023, due to disruptions during the Covid-19 pandemic.

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.

Development of a safe, effective, preventive HIV vaccine remains key to realising a durable end to the HIV/Aids pandemic.

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

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

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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 includes HIV vaccine regimens against a placebo (saline), and a new form of oral pre-exposure prophylaxis (PrEP) against the existing standard for PrEP.

PrEPVacc’s Trial Director Dr Eugene Ruzagira, based at the Medical Research Council, and London School of Hygiene and Tropical Medicine Uganda Research Unit in Uganda said, “They have worked hard and skillfully through very challenging periods during Covid-19 pandemic in order to successfully and safely reach this point.

The study is scheduled to disseminate its findings by December 2024. We have already shared outcomes of our social science work with relevant stakeholders, and we are committed to sharing news about results that emerge from PrEPVacc with the participants and their communities first.”

Participants in PrEPVacc are strongly committed to the study. By the end of their contribution over 17 months after the first vaccine injection, they will have made at least 15 study visits.

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.

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They received information on how best to incorporate PrEP in combination prevention against HIV.

Due to the 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 randomisation of enrolled participants from 1:1:1 to 1:1 and discontinued enrolment to the MVA-combination vaccine arm in all sites by June 2022.

Notwithstanding this change to enrolment, vaccinations and follow-ups have continued as planned in all arms.

The trial minimum enrolment target was revised from 1,668 participants to 1,400, with encouragement to enrol beyond this in anticipation that some participants would miss their second or third vaccines and be excluded from the main vaccine analysis.

The proposal was approved by PrEPVacc’s independent governance committees.

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 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.

They also review study material to check that the language and messages used are simple and acceptable to their communities.
PrEPVacc is led by African researchers from Entebbe in Uganda, at the MRC/UVRI and LSHTM Uganda Research Unit.

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They are supported by 15 partner organisations, six from Africa, six from Europe and three from the US. The Sponsor of PrEPVacc is Imperial College London.

The PrEPVacc study is funded by the European & Developing Countries Clinical Trials Partnership (EDCTP), as part of the EDCTP2 Programme supported by the European Union.

PrEPVacc is a public-private partnership. The EDCTP awarded a €15m grant for the study and all of the institutional partners are providing co-funding through staff salaries. Gilead Inc. and Inovio Pharmaceuticals are giving support to the project through materials and medicines. PrEPVacc is also supported by USAid and Pepfar, USMHRP, SVRI, SAMRC, UKRI, the Wellcome Trust and the Bill and Melinda Gates Foundation.