A California study of Pre-Exposure Prophylaxis ( PrEP ) use amongst gay menthe first conducted in a clinical practice settingshowed no HIV new infections among more than 650 people who were followed for 32 months, according to researchers.
The study, published Sept. 2 in the journal Clinical Infectious Diseases, was conducted by Kaiser Permanente and tracked 657 individuals, 99 percent of whom were men who had sex with men ( MSM ), from 2012-2015.
"Our study is the first to extend the understanding of the use of PrEP in a real-world setting and suggests that the treatment may prevent new HIV infections even in a high-risk setting," said physician and lead author Jonathan Volk, an epidemiologist at Kaiser Permanente San Francisco Medical Center, in a statement. "Until now, evidence supporting the efficacy of PrEP to prevent HIV infection had come from clinical trials and a demonstration project."
Researchers have found that the PrEP intervention is over 90 percent effective at preventing HIV when subjects adhere faithfully to the prescribed regimen, which is usually one daily pill, but those numbers were compiled in clinical trial settings.
Over the 32-month observation period at Kaiser Permanente, there were 1,045 referrals for PrEP and 657 people who began the PrEP regimen, according to the statement; the average age of the users was 37. Compared with people not using PrEP, users were more likely to report multiple sex partners. Of 143 patients who were asked about behavior change after six months of PrEP use, the number of sexual partners was unchanged in 74 percent, decreased in 15 percent, and increased in 11 percent. Condom use was unchanged in 56 percent, decreased in 41 percent, and increased in 3 percent.
Six months after starting PrEP, 30 percent of users had been diagnosed with at least one sexually transmitted infection ( STI ). At 12 months, 50 percent of PrEP users had been diagnosed with any STI; 33 percent had a rectal STI; 33 percent had chlamydia; 28 percent had gonorrhea; and 5.5 percent had syphilis.
"Without a control group, we don't know if these STI rates were higher than what we would have seen without PrEP," said co-author Julia Marcus, a postdoctoral fellow at Kaiser Permanente Division of Research. "Ongoing screening and treatments for STIs, including hepatitis C, are an essential component of a PrEP treatment program."
The researchers also pointed out that, while the study reflected an increased demand for PrEP amongst MSM, health advocates and service providers must continue to reach out to all populations at high risk for HIV infection.