Washington (AFP)

The large clinical trial of a vaccine against HIV, the virus that causes AIDS, conducted by Johnson & Johnson in five countries in sub-Saharan Africa, has been halted for lack of conclusive results, the US pharmaceutical company announced on Tuesday .

This is a big disappointment in the fight against this disease which affects 38 million people worldwide, and against which the search for a vaccine has been unsuccessful for decades.

The trial, named Imbokodo and started in 2017, included around 2,600 young women between the ages of 18 and 35 in Malawi, Mozambique, Zambia, South Africa and Zimbabwe.

Women and girls accounted for 63% of new infections in 2020 in this region.

Some participants received four injections of the vaccine over a year, and others received a placebo.

After two years after the first injection, 51 of the 1,079 participants who received the vaccine had contracted HIV, compared to 63 of the 1,109 participants who received a placebo.

Even though the vaccine was well tolerated, its efficacy was therefore only 25%.

"Based on these results, the Imbokodo trial will not continue," J&J said in a statement.

"While we are disappointed that the vaccine candidate did not provide a sufficient level of protection against HIV infection (...), this study gives us important scientific results for the continued quest for a vaccine against HIV, "said Paul Stoffels, Scientific Director of Johnson and Johnson, quoted in the statement.

J & J's vaccine uses "viral vector" technology - the same one used for its vaccine against Covid-19.

A common type of virus, called adenovirus, is modified to be made harmless and carry genetic information that allows the body to fight off the target virus.

Another trial, named Mosaico, tests a vaccine with a different composition on a different population, men who have sex with men or transgender people, in the United States, South America and Europe, where other strains of the virus are circulating.

This trial will continue, J&J announced.

It is expected to conclude in March 2024.

- Moderna in the ranks -

"Developing a safe and effective vaccine to prevent HIV infection has proven to be a formidable scientific challenge," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAD), said in a statement. American, which partly funded these trials.

"While this is certainly not the result of the study we were hoping for, we must use the knowledge gained through the Imbokodo trial and continue our efforts to find a vaccine that will protect against HIV," he added. .

According to a US government site, Moderna is due to begin trials in September of two HIV vaccines using new messenger RNA technology - used by the US biotech company for its Covid-19 vaccine.

In four decades of AIDS research, researchers have made huge strides.

Access to antiretroviral drugs, which can help keep infected people healthy, has grown.

Those at high risk of infection may take so-called pre-exposure prophylaxis (PrEP) treatment to reduce this risk.

But access to medicines is not equal everywhere, and vaccines have historically been the most effective tools in eradicating infectious diseases.

© 2021 AFP