South Africa has launched a major clinical trial of an experimental vaccine against the AIDS virus, which scientists hope could be the “final nail in the coffin” for the disease.

More than 30 years of efforts to develop an effective vaccine for HIV have not borne fruit, but for the first time since the virus was identified in 1983, scientists said on Wednesday they think they have found a promising candidate.

The new study, known as HVTN 702, will involve more than 5,400 sexually active men and women aged 18-35 in 15 areas around South Africa over four years.