A phase 2 clinical trial of an experimental HIV vaccine in sub-Saharan Africa has been halted after showing only limited protection against the virus. This setback underscores the ongoing challenges in developing an effective HIV vaccine.
Johnson & Johnson has discontinued its phase 2 Imbokodo trial for an HIV vaccine candidate, which failed to provide adequate protection against AIDS. Funded by Johnson & Johnson, the Bill & Melinda Gates Foundation, and the National Institutes of Health, the vaccine used a modified adenovirus called Ad26 to deliver fragments of four HIV subtypes, aiming to trigger an immune response.
Launched in 2017, the trial involved 2,600 young women at high risk of HIV in five sub-Saharan African countries, where nearly two-thirds of global new infections occur. Participants received two initial doses and two boosters over a year. Researchers compared infections from month 7 (one month post-third dose) to month 24.
In this period, 63 of 1,109 placebo recipients contracted HIV, versus 51 of 1,079 vaccine recipients, yielding a 25% efficacy rate. Trial leader Glenda Gray, president of the South African Medical Research Council, noted this level was insufficient and could foster a false sense of security.
HIV remains a global threat, with over 1.5 million new infections in 2020. Another South African trial was halted last year for similar reasons. "I should be used to it by now, but you're never used to it," said Dr. Gray, who has pursued HIV vaccines for over 15 years.
Johnson & Johnson reports a parallel trial using an updated version is underway among men who have sex with men and transgender individuals in eight countries. Meanwhile, Moderna, renowned for its mRNA COVID-19 vaccine, has initiated human trials for an mRNA-based HIV vaccine. This phase will span two years with 56 HIV-negative volunteers aged 18-50.
