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. 2017 Sep 1;65(5):712-718.
doi: 10.1093/cid/cix439.

Incidence of Gonorrhea and Chlamydia Following Human Immunodeficiency Virus Preexposure Prophylaxis Among Men Who Have Sex With Men: A Modeling Study

Samuel M Jenness  1 , Kevin M Weiss  1 , Steven M Goodreau  2 , Thomas Gift  3 , Harrell Chesson  3 , Karen W Hoover  4 , Dawn K Smith  4 , Albert Y Liu  5 , Patrick S Sullivan  1 , Eli S Rosenberg  1
Affiliations

Incidence of Gonorrhea and Chlamydia Following Human Immunodeficiency Virus Preexposure Prophylaxis Among Men Who Have Sex With Men: A Modeling Study

Samuel M Jenness et al. Clin Infect Dis. .

Abstract

Background: Preexposure prophylaxis (PrEP) is highly effective for preventing human immunodeficiency virus (HIV) infection, but risk compensation (RC) in men who have sex with men (MSM) raises concerns about increased sexually transmitted infections (STIs). The Center for Disease Control and Prevention's (CDC's) PrEP guidelines recommend biannual STI screening, which may reduce incidence by treating STIs that would otherwise remain undiagnosed. We investigated these two counteracting phenomena.

Methods: With a network-based mathematical model of HIV, Neisseria gonorrhoeae (NG), and Chlamydia trachomatis (CT) transmission dynamics among MSM in the United States, we simulated PrEP uptake following the prescription indications and HIV/STI screening recommendations in the CDC guidelines. Scenarios varied PrEP coverage (the proportion of MSM indicated for PrEP who received it), RC (a reduction in the per-act probability of condom use), and the STI screening interval.

Results: In our reference scenario (40% coverage, 40% RC), 42% of NG and 40% of CT infections would be averted over the next decade. A doubling of RC would still result in net STI prevention relative to no PrEP. STIs declined because PrEP-related STI screening resulted in a 17% and 16% absolute increase in the treatment of asymptomatic and rectal STIs, respectively. Screening and timely treatment at quarterly vs biannual intervals would reduce STI incidence an additional 50%.

Conclusions: Implementation of the CDC PrEP guidelines while scaling up PrEP coverage could result in a significant decline in STI incidence among MSM. Our study highlights the design of PrEP not only as antiretroviral medication but as combination HIV/STI prevention incorporating STI screening.

Keywords: Chlamydia trachomatis; Neisseria gonorrhoeae; mathematical model; men who have sex with men; preexposure prophylaxis.

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Figures

Table 1.
Table 1.
Gonorrhea and Chlamydia Incidence Rates, Hazard Ratios, Percent of Infections Averted, and Number Needed to Treat on Preexposure Prophylaxis (PrEP) by PrEP Coverage Level and Behavioral Risk Compensation Level among Men Who Have Sex With Men in the United States
Figure 1.
Figure 1.
Percent of infections averted for gonorrhea and chlamydia under varying preexposure prophylaxis coverage and risk compensation levels among men who have sex with men in the United States over 10 years of 250 simulations. Abbreviations: CT, chlamydia; NG, gonorrhea.
Table 2.
Table 2.
Combined Gonorrhea and Chlamydia Incidence Among All Men Who Have Sex With Men and Preexposure Prophylaxis (PrEP) Users, and Proportion of Asymptomatic Sexually Transmitted Infection (STI) Cases and Rectal STI Cases Treated by PrEP STI Screening Interval, Proportion Successfully Treated, and Random Asymptomatic Screening Outside of PrEP
Figure 2.
Figure 2.
Incidence rates, per 100 person-years at risk, of combined gonorrhea and chlamydia infections under varying preexposure prophylaxis (PrEP)–associated sexually transmitted infection screening intervals and proportion of PrEP users screened and treated among men who have sex with men in the United States over 10 years of 250 simulations. Abbreviations: IR, incidence rate; PrEP, preexposure prophylaxis; PYAR, person-years at risk; STI, sexually transmitted infection.
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