The world may be closer than ever to an effective treatment for HIV. Three HIV vaccine trials being conducted all across the world have doctors and scientists optimistic about the prospect of a viable cure, potentially as soon as 2021, according to a new report from NBC News.

HVTN 702 has been underway in South Africa since 2016. It is based on findings and data from a previous trial, RV144, which had the highest success rate of any prior HIV vaccine trial, reducing rates of the disease by roughly 30%. Still, that rate was not considered effective enough and the trial was deemed a failure, albeit the most promising failure yet. The particular vaccine under trial in HVTN 702 has been adapted for the strain of the disease most prominent in South Africa.

Clinical results for this trial are expected in 2020 or 2021. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, was hopeful of the trial’s prospects and said that a vaccine with at least a 50% effectiveness rate would be viable globally.

Another trial, dubbed “Imbokodo,” is also underway in several southern regions of Africa and focuses on heterosexual women, a group at particular risk of HIV in those areas. Imbokodo is attempting to use “mosaic immunogen,” essentially deploying a wider variety of treatments for numerous global strains of the disease. This trial began in 2017.

“The presumption is that a mosaic is going to give you broader coverage,” Fauci stated.

The third and most recent trial, “Mosaico” began in earnest last month and is basing its approach by and large on Imbokodo. While mostly similar to that older trial, Mosaico is being conducted at 57 locations worldwide and has recruited from broader demographics, including gay men and transgender individuals.

“We have three vaccines currently being tested in efficacy trials,” said Dr. Susan Buchbinder, director of the San Francisco-based Bridge HIV program. “And it takes quite a bit to actually be promising enough in the earlier stages of trials to move you forward into an efficacy study.”