CROI 2017 PrEP Study Summary


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For immediate release: February 15, 2017
Contact: National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
(404) 639-8895   |

Study Summary:
Study Suggests STI Testing and Treatment as Part of PrEP Care May Reduce Bacterial STIs among Gay and Bisexual Men

Poster presentation: STI incidence among MSM following HIV pre-exposure prophylaxis: a modeling study


A joint modeling study by The Rollins School of Public Health at Emory University and the Centers for Disease Control and Prevention (CDC) suggests that for gay and bisexual men, pre-exposure prophylaxis (PrEP) for HIV prevention, along with testing for and treatment of sexually transmitted infections (STI), can reduce not only HIV, but also some STIs, even in the presence of some reductions in condom usage.

These findings were presented today at the 2017 Conference on Retroviruses and Opportunistic Infectionsexternal icon (CROI) in Seattle.

CDC recommendspdf icon that people who use PrEP for HIV prevention be tested for bacterial STIs at least once every six months, even if they do not have symptoms, as part of PrEP care. Antibiotic medication can cure some STIs and reduce their spread.

CDC estimates that approximately 492,000 sexually active gay and bisexual men in America are at substantial risk for HIV infection and could benefit from PrEP. Recent evidence suggests that some men may reduce their use of condoms (which prevents both HIV and STIs) when using PrEP (which prevents only HIV).

In this study, led by Samuel Jenness, PhD, assistant professor of epidemiology at Emory’s Rollins School of Public Health, researchers used a model to forecast how many new cases of gonorrhea and chlamydia could be prevented if 10 percent to 90 percent of PrEP-eligible gay and bisexual men began taking PrEP and underwent bacterial STI testing and treatment every six months, as CDC recommends. Researchers also examined how reduced condom use would affect new cases of those STIs among the population.

Their model showed that:

  • More than 40 percent of chlamydia infections and 42 percent of gonorrhea infections would be prevented over the next decade if 40 percent of PrEP-eligible gay and bisexual men took PrEP and were tested twice a year for STIs. This would occur even with a 40 percent reduction in condom use while on PrEP.
  • The estimated reduction in bacterial STI cases was attributed to frequent STI testing as part of well-delivered PrEP care that would increase the early detection of asymptomatic infections that often remain undiagnosed, untreated, and transmitted to sex partners.
  • STI cases would likely increase if STIs went untreated in more than half of PrEP users, suggesting the important role of clinicians to perform this testing for their patients taking PrEP.
  • Increasing STI testing frequency from twice a year to four times a year would not dramatically affect the prevention of chlamydia or gonorrhea – reducing new cases by an additional 5 percent.

CDC’s comprehensive PrEP guidelinespdf icon are an important tool for providers to help their patients protect themselves from HIV and ensure regular STD testing and treatment care. Bridging the PrEP information gap facing many providers is essential to realizing its full prevention potential. About one-third of primary health care providers had not heard of PrEP for HIV prevention as recently as 2015. To bridge this gap, CDC has been leading efforts to educate providers — including publication of 2014 clinical guidelines, step-by-step PrEP checklists and interview guides — as well as supporting a hotline to answer providers’ questions about when and how to offer PrEP.

PrEP’s effectiveness in HIV prevention is well documented. This new study shows the potential impact that following CDC’s clinical guidelines for PrEP can have on bacterial STI prevention and further clarifies the role of PrEP as part of a comprehensive HIV/STI prevention package.


For more information from CDC’s National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, visit


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Page last reviewed: December 21, 2021