HIV Vaccine Trial Stopped Due to Inadequate Protection Against Infection

Johnson & Johnson announced it would discontinue its phase 2b Imbokodo clinical trial because the human immunodeficiency virus (HIV) vaccine regimen did not sufficiently protect against infection in young women in sub-Saharan Africa.

“HIV is a unique and complex virus that has long posed unprecedented challenges for vaccine development because of its ability to attack, hijack, and evade the human immune system,” said Paul Stoffels, MD, chief scientific officer at Johnson & Johnson. “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.”

The proof-of-concept Imbokodo study began in 2017 and included young women in Malawi, Mozambique, South Africa, Zambia, and Zimbabwe at high risk of acquiring HIV. The vaccine regimen was administered to participants through four vaccination visits over the course of 12 months.

Over 24 months of follow-up, 63 of 1109 participants who received placebo, and 51 of 1079 participants who received the vaccine, acquired HIV—demonstrating a vaccine efficacy rate of 25.2%. The investigational vaccine was found to have a favorable safety profile with no serious adverse events, but moving forward with a vaccine that offered just 25% protection could give women a “false sense of security,” Glenda Gray, a South African physician and principal investigator of the trial, told The New York Times.

In sub-Saharan Africa, women and girls accounted for 63% of new infections in 2020.

“In South Africa, the higher rates of HIV incidence means you need something much more potent,” Dr Gray said in The New York Times article. “The kind of immune responses that were induced were just not enough to stop the high attack rates we see in Africa.”

An ongoing Phase 3 Mosaico study, which is testing the safety and efficacy of a different composition of the HIV vaccine regimen, will continue, Johnson & Johnson said. That trial includes men who have sex with men and transgender individuals and is being conducted in the Americas and Europe amid different circulating strains of HIV.

References:

Johnson & Johnson and global partners announce results from Phase 2b Imbokodo HIV vaccine clinical trial in young women in sub-Saharan Africa. News release. Johnson & Johnson; August 31, 2021.

Nolen S. An experimental HIV vaccine fails in Africa. The New York Times. August 31, 2021.