Using the same mRNA technology that broke the mold with effective COVID-19 vaccines, Moderna has developed two vaccines for HIV. The first phase of testing for both could begin as early as Thursday, according to a post on the National Institutes of Health website for clinical trials.

Phase 1 of the vaccine trial will test the vaccines’ safety, as well as measure immunity and antibody responses. If the vaccines prove to be safe, they’ll need to go through additional testing for researchers to determine how effective they are.

Study participants will be adults aged 18-50 who haven’t been diagnosed with HIV. Several universities and institutes are collaborating on the study in addition to the drug maker, including the University of Texas at San Antonio, George Washington University, Fred Hutchinson Cancer Research Center and Emory University. It’s sponsored by the International AIDS Vaccine Initiative.

Creating an effective vaccine for HIV, or human immunodeficiency virus, is difficult, in part because of how our immune systems respond to HIV compared with other viruses, according to the Broad Institute of MIT and Harvard.

Vaccines act like natural infections in the way they stimulate our immune systems to make antibodies and attack a virus. But unlike when it’s responding to a virus like smallpox or polio, the institute reported, our body is “blind” to HIV.

Moderna’s are the first vaccines for HIV to use mRNA technology, which codes our immune systems in a different way than other vaccines. Researchers hope the success of mRNA COVID-19 vaccines will grow to include an HIV vaccine.

A component of the HIV vaccines being tested showed promise in an earlier study, Popular Science reported, prompting Scripps Research and IAVI to partner with Moderna and advance the vaccine with mRNA technology. Another COVID-19 vaccine maker, Johnson & Johnson, is currently testing a vaccine for HIV.

There were 37.7 million people living with HIV globally in 2020, according to United Nations data. About 1.3 million people in the US are living with HIV, according to the US Department of Health and Human Services.

Moderna didn’t immediately respond to a request for comment.