FAQs for PrEPVacc's vaccine result
**See here for the news release announcing the vaccine result**
1. When will participants know whether they received a vaccine or placebo in the study?
Unblinding has begun across the sites. This means informing the study team and participants who was given an active vaccine, and who was given placebo. Unblinding is part of our ethical obligation to participants. Please contact your site if you are keen to know this and have not yet heard from them. https://www.prepvacc.org/contact
2. How long will PrEPVacc participants be followed up for?
For at least two years, with the aim of conducting HIV testing twice yearly to monitor how many people become HIV positive following the trial, and support participants’ access to care and PrEP.
3. Can participants test for HIV now at any local clinic?
For about four fifths of participants in PrEPVacc, yes, they can test for HIV at any local clinic.
When exiting the study, one fifth of all participants, which is about a quarter of participants allocated to an active vaccine regimen displayed evidence of Vaccine-Induced Sero-Positivity (VISP). VISP occurs when the body has produced antibodies after receiving an HIV vaccine, and following this, HIV test results can be positive even if an individual is not infected with HIV.
For the participants who have evidence of VISP, PrEPVacc will offer an HIV testing service to ensure they receive an accurate diagnosis. Your trial site will tell you if this applies to you.
4. What HIV prevention tools are available to PrEPVacc study participants now? How should participants access these now?
During the trial, counselling on methods of HIV prevention, promotion and provision of PrEP were emphasised at every visit to all participants, with active follow-up regarding use. The number of PrEP providers increased substantially while the trial was underway and PrEP is now available close to all centres. Your trial site will continue to provide counselling and promotion of PrEP and facilitate linkage to local PrEP providers for at least two years for all participants.
5. Are participants who acquired HIV during the trial receiving antiretroviral therapy?
With the exception of one participant who is still not willing to return to the trial site, participants who acquired HIV during the trial have all been counselled and referred for treatment to access the free drugs. Where they have chosen to take it up, they are on standard of care Anti Retroviral Therapy (ART) per their country’s guidelines, free of charge.
6. What do the trial results mean for participants in other HIV vaccine clinical trials?
The results of PrEPVacc have been disseminated and shared with researchers, stakeholders and community members globally so they are aware, and we will collaborate globally to better understand the results.
7. Why did the vaccines not work? How come some people on the active vaccine had antibodies but did not get protection from acquiring HIV?
We know that the vaccines stimulated immune responses, but these did not protect people from acquiring HIV. Only one of several HIV vaccine trials has seen any protection, even though they all stimulated immune responses.
8. More people acquired HIV in the vaccines groups than the placebo groups. Does this mean the vaccine caused HIV?
No. It is not possible to acquire HIV infection directly from the vaccines used in this study.
9. What are the reasons for the differences in incidence rates?
PrEPVacc investigators cannot draw a definitive conclusion on how to interpret the differences in HIV incidence rates in the trial. The difference may be due to chance, but we have to consider the possibility the result is real. The PrEPVacc team is discussing plausible reasons to investigate further with international colleagues.
So far, the PrEPVacc investigators have looked at self-reported PrEP adherence, risk behaviours and statistical errors and none of these account for the differences seen between the vaccine groups. Measurement of PrEP adherence based on drug levels in biological samples is underway.
10. What lessons have been learnt? What would PrEPVacc investigators do differently in the next trial?
We believe that PrEPVacc has been a well-designed and well-conducted study, meeting international standards of best practice and upholding the ethical and regulatory requirements expected of us by national agencies. It successfully navigated the challenges posed to a major clinical trial by the COVID-19 pandemic. A lot of care goes into the preparation leading into any trial to minimise risk and our experience in PrEPVacc shows why this must be the case for all future vaccine trials.
PrEPVacc has reinforced the importance of strong, open and transparent participant and community relationships, without which HIV prevention research cannot move forward.
The data and findings from the social science research which have been published and shared throughout the trial provided valuable insights that improved the conduct of the trial, and the benefits of integrating these methods in biomedical studies is an important lesson for future trials.
Despite the small size of the trial, PrEPVacc has efficiently answered the key questions of vaccine efficacy for two separate vaccine combination arms. It was the first HIV vaccine efficacy trial that conducted the main immune assays in an African lab and the first to host the trial database in Africa. PrEPVacc is the first HIV vaccine efficacy trial to be conducted in East African countries, and it has advanced community and African leadership of complex multi-country HIV vaccine trials.
11. Will PrEPVacc work on other vaccines?
PrEPVacc was a study to test two specific vaccine regimens and it will stop at the end of 2024. It will not test other vaccines, but the team members who worked on PrEPVacc are already joining new initiatives to develop HIV vaccines, for example the BRILLIANT programme in Uganda and South Africa.
12. Why are the PrEP results not ready at the same time? Why have they taken longer?
The vaccine trials and the PrEP trial are separate analyses. We needed to get the vaccine result first as that informs the background incidence (the number of new HIV infections in each group) which we need to know for the PrEP analysis. We also need to know the drug levels during the study PrEP period and this laboratory work is ongoing. PrEPVacc’s oral PrEP results are expected to be announced later in 2024 and we will again be contacting stakeholders, participants and collaborators about these results just before or in parallel to announcement in public.
Last updated: 5 August 2024