Insights: Pre-Exposure Prophylaxis (PrEP) and STIs

PrEP is a medication that can be used to help prevent human immunodeficiency virus (HIV) infection. Research has shown that when taken consistently, daily PrEP can reduce the risk of HIV infection by up to 90%. The Center for Disease Control and Prevention (CDC) has recommended that PrEP be offered to individuals who are at high risk of getting HIV, including those who inject drugs, those who are HIV-negative but are in a sexual relationship with someone who is HIV-positive, and gay or bisexual men who have engaged in anal sex without a condom and are not in a monogamous relationship.

Having an STI could also increase the risk for HIV infection. The two most commonly reported STIs in the United States, Neisseria gonorrhoea (NG) and Chlamydia trachomatis (CT), increase both the risk for transmission and acquisition of HIV among men who have sex with men (MSM). Recent research by Emory’s Coalition for Applied Modeling for Prevention (CAMP) estimated that 10% of all new HIV infections among men who have sex with men (MSM) are linked to NG and CT. Offering PrEP to MSM at the time of NG/CT diagnosis is an effective and efficient way of targeting PrEP use to those at high risk for getting HIV. This targeted PrEP approach was estimated by CAMP researchers to be 1.6X as impactful as untargeted PrEP screening in preventing HIV infection among MSM. Expanding NG/CT screening for MSM at the community level and offering PrEP to those testing positive for NG/CT could reduce HIV incidence by 22% over 20 years.

Because PrEP does not prevent STIs, the public health community is concerned that individuals on PrEP may falsely perceive that they are “protected” in their sexual risk behaviors, leading to risk compensation (an increase in risk behaviors while taking PrEP) and higher rates of STIs. Current CDC PrEP guidelines recommend at least bi-annual STI screening following PrEP initiation. In addition, the guidelines recommend quarterly STI testing for sexually active persons with signs or symptoms of infection and asymptomatic MSM at high risk for recurrent bacterial STIs. Based on the modeling work by CAMP researchers, implementing the CDC PrEP guidelines with bi-annual STI screening alone could prevent 40% of new NG/CT infections over the next 10 years, and with the additional quarterly STI screening of MSM at high risk for recurrent bacterial STIs, it could reduce STI incidence even further. Diagnosis and treatment of asymptomatic NG/CT could increase 17% due to PrEP-related screening.

NG/CT diagnosis has been identified as an efficient, objective indicator of PrEP eligibility. Targeting PrEP to MSM at time of NG/CT diagnosis and implementing the CDC PrEP guidelines – with the recommended follow-up STI screening – will not only reduce the burden of HIV, but also significantly decrease STI incidence.


  • U.S. Department of Health and Human Services. HIV Prevention. AIDSinfo.–prep- Published November 7, 2018. Accessed March 5, 2019.
  • Centers for Disease Control and Prevention. PrEP. Centers for Disease Control and Prevention.  Accessed March 5, 2019
  • Jenness SM, Weiss KM, Goodreau SM, et al. Incidence of Gonorrhea and Chlamydia Following Human Immunodeficiency Virus Preexposure Prophylaxis Among Men Who Have Sex With Men: A Modeling Study. Clin Infect Dis. 2017;65(5):712-718.
  • Jones J, Weiss K, Mermin J, et al. Proportion of Incident HIV Cases among Men Who Have Sex with Men Attributable to Gonorrhea and Chlamydia: A Modeling Analysis. Sex Transm Dis. 2019.
  • Kasaie P, Schumacher CM, Jennings JM, et al. Gonorrhoea and chlamydia diagnosis as an entry point for HIV pre-exposure prophylaxis: a modelling study. BMJ Open. 2019;9(3):e023453.

About Kim Rodgers

Kim Rodgers serves as a Communications Specialist at NACCHO. Her work includes promoting local health departments' best practices, as well as partner tools and resources, in infectious disease and preparedness through NACCHO's communications channels, storytelling, and outreach to various audiences.

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