Assessing the Impact of HIV Preexposure Prophylaxis Scale-Up on Gonorrhea Incidence among Gay and Bisexual Men in Sydney: A Mathematical Modeling Study

Michael L. Walker, David Stiasny, Rebecca J. Guy, Matthew G. Law, Martin Holt, Limin Mao, Basil Donovan, Andrew E. Grulich, Richard T. Gray*, David G. Regan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Background The rollout of preexposure prophylaxis (PrEP) for HIV prevention among gay and bisexual men (GBM) is associated with increases in condomless anal intercourse, potentially increasing the incidence of other sexually transmissible infections (STIs). Methods We developed an individual-based mathematical model to simulate the transmission of Neisseria gonorrhoeae among GBM in Sydney, accounting for changes in sexual practices, STI testing, and PrEP use. We calibrated and validated the model using reported incidence rates for HIV-positive and HIV-negative GBM from 2010 to 2019. Scenarios were run with varying PrEP uptake, PrEP-related STI testing, and PrEP-related sexual behavior and testing intervals up to 2030 to assess the impact of PrEP use on gonorrhea incidence. Results Preexposure prophylaxis uptake and associated 3-monthly STI testing from 2015 onward resulted in a predicted increase from 20 to 37 N. gonorrhoeae infections per 100 person-years among HIV-negative GBM by the end of 2020. This is lower than the counterfactual predictions of 45 per 100 person-years if PrEP were not scaled up and 48 per 100 person-years with nonadherence to 3-monthly STI testing. Increasing the time between STI tests for PrEP users by 1 month from 2018 results in the incidence rate among HIV-negative GBM increasing by 8% by 2030. If PrEP coverage doubles from 24% to 53%, incidence among HIV-negative GBM declines by 25% by 2030. Conclusions Behavior change due to widespread PrEP use may lead to significant increases in gonorrhea incidence in GBM, but the recommended quarterly STI testing recommended for PrEP users should reduce incidence by 18% by 2030.

Original languageEnglish
Pages (from-to)534-540
Number of pages7
JournalSexually Transmitted Diseases
Issue number8
Publication statusPublished - 1 Aug 2022
Externally publishedYes

Bibliographical note

Funding Information:
Conflict of Interest and Sources of Funding: The authors do not have any conflicts of interest to declare. This project was funded by a New South Wales Ministry of Health Prevention Research Support Program and a National Health and Medical Research Council Project Grant (ID 1145642).

Funding Information:
Acknowledgments: High-performance computing resources and services were provided by the Australian government–funded National Computational Infrastructure. The authors acknowledge Research Technology Services at UNSW Sydney for providing additional computing and consulting resources, including use of the computational cluster Katana and project support (TG182837) for D. Stiasny. The authors also acknowledge Heath Paynter, representing the AIDS Council of New South Wales, for providing feedback on the manuscript. The Kirby Institute is funded by the Australian Government Department of Health and is affiliated with the Faculty of Medicine, UNSW Sydney. The views expressed in this publication do not necessarily represent the position of the Australian Government.

Publisher Copyright:
© Lippincott Williams & Wilkins.


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