The decades-long research for an HIV vaccine has hit another setback after another vaccine candidate failed in a large-scale African study.
On Tuesday, Johnson & Johnson (J&J) announced that its four-year investigation, known as the “Imbokodo trial”, which involved 2,600 women in SA and its four neighbouring countries — Zimbabwe, Mozambique, Malawi and Zambia — offered no convincing protection against HIV infection in the trial. The study will, as a result of this, be discontinued.
Researchers say the 25% efficacy shown by the experimental vaccine was too low to make it useful. No safety concerns were reported.
In these countries, women and girls account for about 60% of all new infections.
“Though this is certainly not the study outcome for which we had hoped, we must apply the knowledge learnt from the Imbokodo trial,” said Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases (NIAID), which funded the study along with the Melinda Gates Foundation.
The Imbokodo trial, which uses the same adenovirus platform used in J&J's Covid-19 shot, started in 2017 in about 26 sites across the five African countries. It is based on “mosaic” immunogens—vaccine components designed to induce immune responses against a wide variety of global HIV strains. The vaccine candidate used a strain of common-cold virus (adenovirus serotype 26, or Ad26), engineered to not cause illness, but to deliver antigens to spur an immune response.
Earlier research indicated the vaccine was both well-tolerated and could induce an anti-HIV immune response. Imbokodo participants received four vaccinations during a one-year period. This included four doses of the investigational quadrivalent vaccine. J&J said it would, however, continue with a companion study, the Phase 3 Mosaico trial, which is testing the safety and efficacy of a different investigational HIV vaccine among men who have sex with men and transgender populations in the US and Europe. The Mosaico study is expected to be completed in March 2024.