SAN DIEGO (FRONTLINE MEDICAL NEWS) – Increased use of pre-exposure prophylaxis (PrEP) to prevent HIV transmission has accelerated but is not the main reason for surging rates of sexually transmitted infections in the United States, Kenneth Mayer, MD, said during an oral presentation at an annual scientific meeting on infectious diseases.

Public health officials are seeing unprecedented rises in STIs such as syphilis and gonorrhea in both HIV-negative and HIV-positive individuals, and these trends predate the advent of PrEP, said Dr. Mayer of the Fenway Institute and Harvard University in Boston, Mass. “An overall level of behavioral disinhibition is fueling this epidemic and is not necessarily associated with PrEP,” he said.

In the United States, de novo uptake of PrEP rose sevenfold between the third quarters of 2012 and 2016, noted Dr. Mayer. But rather than considering PreP a red flag for high-risk behavior, providers should use it as an opportunity to increase early diagnosis of STI, he said. Instead of siloing HIV and STI testing and management, they can advocate for more “user-friendly” approaches, such as housing PrEP and proactive STI screening under one roof, offering home-based testing for HIV and STIs, and supporting phone apps that educate high-risk individuals and link them to screening and treatment, he said.

Several studies suggest that being on PrEP does not increase the likelihood of acquiring or transmitting an STI, Dr. Mayer emphasized. In the open-label PROUD trial of PrEP in men who have sex with men (MSM), “rates of STI were extremely high and remained so, but did not go up after PrEP was initiated,” he noted. Importantly, the incidence of HIV infection was only 1.6 per 100 person-years when MSM received PrEP immediately but was 9.4 cases per 100 person-years when MSM were randomly assigned to a 1-year wait list (rate ratio, 6.0). In the randomized ANRS IPERGAY trial, 70% of high-risk MSM prescribed PrEP reported engaging in condomless anal intercourse during their most recent sexual encounter, but that proportion remained stable over 24 subsequent months of follow-up.

Providers also should understand that oral PrEP is just as effective at preventing HIV transmission when patients have STIs, Dr. Mayer said. In five recent studies, PrEP was equally efficacious among MSM regardless of whether they had syphilis or other STIs, and bacterial vaginosis in women also did not decrease the efficacy of oral PrEP. “There is no evidence to indicate that the efficacy of PrEP is lower among persons with STIs,” Dr. Mayer said.

Finally, providers should consider screening high-risk individuals for STIs more frequently than every 6 months as recommended by the Centers for Disease Control and Prevention, said Dr. Mayer. “For men who have sex with men, who are sexually active, and are on PrEP, quarterly screening makes exceedingly good sense from a cost-effectiveness standpoint,” he said.

“Screening less frequently than quarterly means that these individuals are having STIs for a longer period of time. When they are sexually active, we have a better chance of interrupting the transmission chain if we detect closer to the time of infection.”

Dr. Mayer disclosed support from the National Institutes of Health and Gilead Sciences, which makes some of the medications used in PrEP regimens.