A vaccine that would seek to exploit a weakness in the HIV virus is going to undergo a major trial in South Africa soon. Researchers will start vaccinating thousands of volunteers this coming week, and if the trial is successful, it would mean a major step forward in fighting the virus that causes AIDS.

This is only the seventh full-scale human trial for HIV, which infects 2 million people around the world. Researchers say this would be a “historic” event for HIV if it were to show some efficacy. To do that, the vaccine would have to prove 50 percent to 60 percent effective, which would enable Sanofi Pasteur and GSK to start licensing negotiations with the government of South Africa.

And once it starts working in South Africa, scientists think it could be adjusted to fight viral subtypes elsewhere, including the United States. A total of 5,400 HIV-negative people have been recruited, and will receive five injections over the course of a year, followed by two years of monitoring.

“For the first time in seven years, the scientific community is embarking on a large-scale clinical trial of an HIV vaccine, the product of years of study and experimentation,” said Anthony S. Fauci, M.D., director of NIAID, part of the National Institutes of Health and a co-funder of the trial, in a statement from the National Institute of Allergy and Infectious Diseases released earlier this year. “A safe and effective HIV vaccine could help bring about a durable end to the HIV/AIDS pandemic and is particularly needed in southern Africa, where HIV is more pervasive than anywhere else in the world.”