Most seeking medication to prevent HIV transmission have used the daily pill Truvada, more commonly referred to as PrEP. But a successful trial showed that a single shot taken every two months can be more successful in preventing the disease.

The drug, called cabotegravir, was tested by Viiv Healthcare in a trial conducted by the H.I.V. Prevention Trials Network. It included nearly 4,600 cisgender men and transgender women who have sex with men (it has not yet been tested on trangender women) in a total of seven countries. Reports The New York Times:

Each of the participants got a shot every two months, either cabotegravir or a placebo. Each participant also took either Truvada or a placebo pill every day. (A separate study of cisgender women in sub-Saharan Africa was designed at the same time, but it has taken longer to enroll participants.)

The trial was expected to continue well into 2022, but it was stopped in May after an interim analysis showed that cabotegravir was highly effective.

Results showed that the shot was 66 percent more effective than Truvada in preventing HIV transmission.

“I think it’s revolutionary,” Dr. Rochelle Walensky, a researcher at Harvard University, told The Times about the findings. “It’s exciting to have another pharma company in the PrEP mix. This will create competition and ideally drives costs down.”

Per The Times:

For its trial, Viiv Healthcare mandated that at least half of the participants were Black men who have sex with men, the group most severely affected by H.I.V. in the United States. “That makes this the largest interventional study” in this population, said Dr. Kimberly Smith, head of research and development at Viiv.

As Colorlines previously reported, in 2017, Black men who have sex with men accounted for 26 percent (10,070) of the 38,739 new HIV diagnoses and 37 percent of new diagnoses among all gay and bisexual men in the United States and dependent areas, according to the Centers for Disease Control and Prevention (CDC). It is projected that half of all Black men who have sex with other men will be diagnosed with HIV in their lifetime.

According to the CDC, around one in four people living with HIV is a woman. Among all women, Black women are disproportionately more likely to receive a diagnosis; they are diagnosed at 15 times the rate of white women.

While PrEP has proven to cut HIV transmission rates, The Times writes, “Many people are unable or unwilling to take a daily pill to prevent HIV infection, particularly in low-income countries where the coronavirus pandemic is disrupting services and access to antiretroviral drugs.”

The Times reports that the company behind the shot is expected to file for F.D.A. approval in early 2021.