Human immunodeficiency virus (HIV) is a blood-borne virus typically transmitted via sexual intercourse and shared intravenous needles. Since the beginning of the epidemic, almost 70 million people have been infected with the HIV virus and about 35 million people have died of AIDS. Sub-Saharan Africa remains the most severely affected area, with nearly one out of 20 adults living with HIV and accounting for 69% of the people living with HIV worldwide

South Africa is particularly poised as a key driver of HIV vaccine innovation, since it has the highest incidence of the disease and is well-equipped with world-renowned researchers and infrastructure to conduct HIV studies. The in-country partners along with HVTN sites provide primary and follow-up care to communities involved in clinical trials. They educate the local communities and raise awareness about HIV and vaccine trials.

This consortium of public and private organizations committed in 2010 to building on the success of the RV144 HIV vaccine trial*, which showed a protective effect, to move forward with a new trial currently in phase IIb/III. The P5 aims to produce an HIV vaccine that could have a significant public health benefit in southern Africa and to deepen scientists’ understanding of the immune responses associated with preventing HIV infection.

The P5 strategy for a prophylactic HIV vaccine is driven by the RV144 results and by subsequent post-hoc analyses. The strategy is based on the evaluation of a regionally adapted RV144-like vaccine regimen in South Africa, aiming at improving the efficacy observed in RV144 by the use of a more potent adjuvant (MF59) and the addition of booster doses at 12 and 18 months from first immunization. The goal of the P5 is to at least replicate the early efficacy observed in RV144 and extend its durability to meet the Target Product Profile of 50% vaccine efficacy over a 24 month period.

The preliminary results of a study performed in healthy volonteers (HVTN100) showed that all fully vaccinated candidates developed a strong humoral and cellular immune response. These results published in 2018 in the Lancet HIV (DOI:https://doi.org/10.1016/S2352-3018(18)30095-X) supported the initiation of a large-scale Phase 2b/3 study which is currently ongoing in South Africa (HVTN 702). Preliminary results are expected in 2021 and final results will be released by Q2 2022.

* The HIV vaccine Phase III trial, RV144, conducted in Thailand by US-Army led partnership showed for the first time that an HIV vaccine is feasible. Although efficacy results were modest, this study provided the first evidence that a safe and preventive HIV vaccine was possible for humans. Post-hoc analyses of this study provided a correlation of risk that could be used to substantiate and expand upon such results.

(Sources: WHO factsheet accessed on April 16, 2019: http://www.who.int/mediacentre/factsheets/fs100/en/; WHO, Global Health Observatory (GHO) accessed on April 16, 2019: http://www.who.int/gho/hiv/en/)