Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP), which remains unapproved in the United Kingdom, could dramatically reduce new infections among men who have sex with men (MSM) living there. Publishing their findings in The Lancet, researchers used mathematical models to project the ability of various interventions to prevent HIV among 15-to-64-year-old U.K. MSM between 2014 and 2020.

Those interventions included expanded HIV testing, test-and-treat programs that harness the power of HIV treatment to prevent the spread of the virus, PrEP, and sexual behavioral changes.

The status quo, the researchers estimated, would result in 16,955 new HIV infections by 2020. A scenario in which up to 50 percent of MSM tested twice a year would be the most effective single intervention to reduce HIV incidence among the population. If PrEP were only targeted at high-risk men, this would prevent an estimated 9,955 (59 percent) projected infections. A program offering PrEP along with regular testing and treatment to those who test positive, even if the program included only a quarter of high-risk MSM, could prevent an estimated 7,400 (44 percent) new cases of HIV before 2020.

“Current prevention efforts in the U.K. that focus on correct and consistent condom use and regular HIV testing have been falling short,” the study’s lead author, Narat Punyacharoensin, PhD, who conducted the research at the London School of Hygiene & Tropical Medicine, said in a press release. “HIV rates among men who have sex with men remain high with around 2,800 men who have sex with men becoming infected with HIV in 2014, and the trend shows no sign of abating. Our results show that pre-exposure prophylaxis offers a major opportunity to curb new infections and could help reverse the HIV epidemic among men who have sex with men in the U.K.”

The researchers also projected that even if there were a substantial increase in sexual risk-taking among MSM on Truvada (a phenomenon known as risk compensation), this would reduce the effect of PrEP but not likely nullify its protective factor.

The researchers concluded that “PrEP could prevent a large number of new HIV infections if other key strategies including HIV testing and treatment are simultaneously expanded and improved. Without PrEP, HIV incidence in MSM in the U.K. is unlikely to decrease substantially by the end of this decade.”

To read a press release about the study, click here.

To read the study abstract, click here.