Johnson & Johnson’s long-awaited HIV vaccine failed to demonstrate adequate protection in a clinical trial involving young women in sub-Saharan Africa, the company and US health authorities said Tuesday.

Although the vaccine was found to have no serious side effects, its effectiveness in preventing HIV infection was just over 25%.

As a result, the so-called “Imbokodo” trial, which began in 2017 and included some 2,600 women between the ages of 18 and 35, will be stopped and participants from Malawi, Mozambique, South Africa, Zambia and Zimbabwe will be informed if they received the vaccine or the placebo.

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

Paul Stoffels, Scientific Director of J&J, thanked both the women who participated in the trial and the laboratory partners in a statement.

“While we are disappointed that the vaccine candidate did not provide a sufficient level of protection against HIV infection in the Imbokodo trial, the study will give us important scientific findings in the ongoing pursuit for a vaccine to prevent HIV,” he said.

“We must apply the knowledge learned from the Imbokodo trial and continue our efforts to find a vaccine that will be protective against HIV,” added Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases which co-funded the study.

However, the laboratory will continue with a parallel trial in men who have sex with men and transgender individuals that is conducted in the Americas and Europe, where the composition of the vaccine differs as do the prevalent strains of HIV. This test is expected to conclude in March 2024.

In the four decades since the first cases of what would become known as AIDS were documented, scientists have made great strides in treating HIV, turning what was once a death sentence into a manageable condition.