Experimental HIV vaccine fails in Africa, but there is still hope

A Phase 2 clinical trial of an investigational HIV vaccine in sub-Saharan Africa has just been halted, with data showing that injections offered only limited protection against the virus. This new failure testifies once again to the complexity of this pathogen which never ceases to challenge modern medicine.

Pharmaceutical giant Johnson & Johnson has just indicated the end of its phase 2 clinical trial of its latest vaccine candidate against the human immunodeficiency virus (HIV), which does not offer sufficient protection against AIDS . The serum, whose development was funded by Johnson & Johnson, the Bill and Melinda Gates Foundation and the National Institutes of Health, was based on an adenovirus called Ad26.

The pathogen had been engineered to carry fragments of four HIV subtypes around the body in hopes of eliciting an immune response against future infections.

An insufficient rate of effectiveness against HIV

During this trial, which began in 2017, called Imbokodo, the experimental vaccine was administered to 2,600 young women deemed to be at high risk of HIV infection in five countries in sub-Saharan Africa. This sample represents almost two-thirds of new HIV infections in the region.

The participants received two initial injections and two booster doses over the course of a year. The researchers then analyzed the number of new infections in the sample and in a placebo group between the seventh month (one month after the third dose) and the 24th month.

During this time, 63 of the 1,109 participants who received the placebo became infected with HIV, compared to 51 of the 1,079 participants who received the vaccine, resulting in an efficacy rate of 25%. For the authors, this was insufficient and even potentially dangerous. A vaccine that offers only 25% protection could indeed give women a “false sense of security,” said Glenda Gray, the trial’s principal investigator, to The Times.

hiv aidsA cell infected with HIV / Credits: NIAID

Other battles to come

This is unfortunately not the last battle lost against this virus which, again in 2020, would have infected more than 1.5 million additional people.

Another trial was also halted last year in South Africa for lack of efficacy. “I should be used to it by now, but you’re never used to it, you always put your heart and soul into it,” argues Dr Gray. The researcher, who is also president of the South African Medical Research Council, has been working on the development of an HIV vaccine for more than fifteen years.

In the meantime, other battles are brewing. According to Johnson & Johnson, a parallel trial based on a different iteration of the latter vaccine is ongoing. It is being tested on men who have sex with men and transgender people in eight countries.

Moderna, which has distinguished itself with its mRNA vaccine against the SARS-CoV-2 coronavirus. just announced the launch of human tests for an HIV vaccine based on the same technology. This first stage will take place over two years. It will involve 56 HIV-negative volunteers aged 18 to 50.

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