Johnson & Johnson halted a mid-stage trial of its HIV vaccine in southern Africa after the injection showed insufficient ability to protect people from contracting the virus.
The trial, called Imbokodo, showed that the vaccine was only 25% effective in preventing HIV infection over a two-year period, below the target of 50% efficacy, according to a statement. A similar vaccine developed by the drugmaker will continue to be tested in Europe and America in a final-stage study called Mosaic, said Paul Stoffels, J & J’s chief scientific officer.
The discontinuation of the study is another setback in efforts to control HIV, a treatable but potentially deadly disease that affects nearly 38 million people worldwide. About 1.5 million were infected last year. While people can live healthy lives with the virus, prevention with a vaccine still seems tantalizingly out of reach.
“With vaccines, it seems very difficult to do,” Stoffels said in an interview. “The virus integrates almost immediately into the body and it is very difficult to create immune protection.”
That African study enrolled about 2,600 women in five countries in the southern part of the continent, where HIV infection is extremely common and is often transmitted through heterosexual contact. Imbokodo began enrolling participants in 2017, focusing on women at high risk of contracting HIV.
Like J & J’s Covid vaccine, the HIV vaccine uses a cold virus that is modified to generate an immune response against the AIDS virus. The participants received a total of four injections, two of the vaccine and two booster injections that contained HIV proteins that were expected to further exacerbate the immune response.
The study’s goal of 50% efficacy was set at a level that could “change the future of the HIV pandemic,” Stoffels said. “You won’t get that with 25%.”
However, the second study of the related vaccine will continue, as it is different enough that it still has a chance of success, Stoffels said. The Mosaic study enrolled a population where the spread of HIV is less intense and transmission patterns are different. Patients receive six injections of a vaccine regimen that has a slightly broader spectrum, he said.
Despite the setback, Stoffels said he is optimistic that the vaccine’s limited efficacy may help scientists move toward a treatment that is more effective. The immune responses of study participants will be analyzed to better understand why some were protected and others were not, he said.
The disappointments of the HIV vaccine date almost back to the initial discovery of the disease in humans. Margaret Heckler, who at the time was the US Secretary of Health and Human Services, said in 1984 that an injection to prevent HIV would be ready for testing within two years. Investigators have pursued the goal ever since.
© 2021 Bloomberg