For the first time, researchers have concluded that Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis (PrEP) is independently associated with a significant decline in U.S. HIV diagnoses.

Investigators obtained 2012 to 2016 HIV diagnosis data from all 50 states plus the District of Columbia as well as viral suppression rates among people with HIV from 37 states plus DC. For PrEP use statistics, the study authors relied on a national prescription database representing at least 83 percent of all prescriptions dispensed by commercial pharmacies.

The national U.S. diagnosis rate per 100,000 people age 13 and older declined from 15.7 diagnoses in 2012 to 14.5 diagnoses in 2016, for an estimated average decline of 1.6 percent per year.

The national PrEP use rate per 1,000 people considered good PrEP candidates according to the Centers for Disease Control and Prevention’s criteria was 7.0 in 2012 and increased to 68.5 in 2016, for an estimated average increase of 78 percent per year.

PrEP use rates varied widely from state to state during the study period. In the 10 states in the top 20 percent of PrEP use, the HIV diagnosis rate declined by an estimated 4.7 percent per year, while the bottom 10 states saw an estimated 0.9 percent annual increase in their HIV diagnosis rate.

The researchers adjusted these HIV diagnosis figures to account for the slight increase in viral suppression rates among U.S. residents with HIV (fully suppressing the virus prevents transmission) during the study period. They concluded that PrEP’s association with HIV diagnosis rates remained statistically significant, meaning it is unlikely to have occurred by chance.

PrEP use has continued to increase rapidly since 2016—Gilead Sciences estimates that 180,000 U.S. residents are currently on it—so it is likely that Truvada is having even more of an impact on the HIV epidemic today.

“These data further validate the potential for significant public health impacts of Truvada for PrEP to help reduce HIV transmission in the U.S.,” says Patrick Sullivan, a professor of epidemiology at the Rollins School of Public Health at Emory University in Atlanta and the study’s lead author. “Our analysis emphasizes the importance of improving access to HIV screening and a full range of prevention tools, including PrEP, in U.S. states.”