The latest trial of a vaccine against HIV, the virus that causes AIDS, has been halted as results show it is not working.
The Maryland-based U.S. National Institutes of Health announced Monday it has stopped the HVTN 702 study in South Africa, following a recommendation of an independent data and safety monitoring board.
The study, also called Uhambo — meaning travel or a journey in Zulu — enrolled 5,407 HIV-negative volunteers at 14 sites across South Africa beginning in 2016. Participants were sexually active men and women between the ages of 18 and 35, who were randomly assigned to receive six injections of either the investigational vaccine regimen or a placebo.
Over a period of 18 months, enough time for the vaccine regimen to stimulate an immune response, there were 129 HIV infections among the vaccine recipients and 123 HIV infections among the placebo recipients. The findings showed there wasn't significant evidence that vaccination either decreased or increased infection rates.
The trial in South Africa was based on an earlier trial in Thailand, the RV144 clinical trial, the only vaccine that has ever shown any degree of success in protection from HIV. Scientists say they will continue to study the results of the HVTN 702 trial, to find out why the vaccine that had modest efficacy in Thailand didn't work in South Africa. Researchers said there were no safety concerns about the vaccine itself.
Experts have voiced disappointment in the decision to stop the vaccine trial in South Africa.
"Whilst this is a significant setback for the field, we need to continue the quest for a preventive vaccine. The rates of HIV infection, which continue unabated in this region, should spur greater urgency, global attention and investment to the quest," said Linda-Gail Bekker, past president of the International AIDS Society and chair of the Enterprise Advisory Group.
"An HIV vaccine is essential to end the global pandemic, and we hoped this vaccine candidate would work. Regrettably, it does not," said Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, which is part of the NIH.
South Africa has one of the world's highest HIV rates. According to UNAIDS, more than 20 percent of people between the ages of 15 and 49 were HIV-positive in 2018.
Multiple HIV vaccines have been tested since the 1990s.
