By Ethan Covey
Data from a large Australian study have found that widespread implementation of HIV pre-exposure prophylaxis (PrEP) does not lead to increases in sexually transmitted infections (STIs) among gay and bisexual men.
This population-level study refutes findings from implementation trials that have demonstrated increased PrEP can be correlated with increasing rates of bacterial STIs (Lancet Infect Dis 2022;22[8]:P1231-P1241).
“This study represents the largest group of PrEP users monitored for STIs over time globally, and gives us a unique opportunity to explore the impact of large-scale PrEP implementation on STIs in the community,” Michael W. Traeger, MSc, a PhD candidate at the Burnet Institute, in Melbourne, Australia, and the lead author of the study, told Infectious Disease Special Edition.
The study utilized data from HIV-negative gay and bisexual men aged 16 years and older who had been prescribed PrEP across a large network of 37 clinics across Australia between Jan. 1, 2016—when widespread PrEP implementation began—and Dec. 31, 2019. A total of 22,730 men were included in the analyses.
Using this large data set, the researchers were able to monitor STIs among the majority of gay and bisexual men using PrEP in Australia. Cases of chlamydia decreased from a rate of 48.7 per 100 person-years during July through December 2016, to 42.0 cases per 100 person-years from July through December 2019. Gonorrhea incidence also declined, from 45.5 cases per 100 person-years from July to December 2016, to 37.2 cases per 100 person-years from July to December 2019. Declines in both chlamydia and gonorrhea were strongest during the initial 18 months of observation and then stabilized.
“Our analysis shows that over four years of PrEP implementation in Australia, rates of STIs such as chlamydia and gonorrhea have mostly stabilized among people who use PrEP,” Dr. Traeger said.
Incidence of syphilis increased slightly during the study period, from 6.2 cases per 100 person-years in July through December 2016, to 9.8 cases per 100 person-years from July to December 2019.
“While rates of syphilis were lower than chlamydia and gonorrhea overall, syphilis incidence did slightly increase during the study period,” Dr. Traeger added. “Syphilis trends are likely influenced by a number of interacting factors, including changes in sexual networks following PrEP implementation.”
Overall, Dr. Traeger noted, the trends are likely influenced by the changing profile of people starting PrEP over time. “For example, people who accessed PrEP early from large demonstration studies likely have a different risk profile to those starting PrEP since it was listed on the Pharmaceutical Benefits Scheme.
“Importantly,” he added, “the data highlight that PrEP implementation in Australia has not led to exponentially increasing STI rates, and that PrEP users are tested for STIs frequently. Our findings support the continued implementation of PrEP programs internationally. It will be important to continue to monitor STIs among gay and bisexual men in the context of further PrEP uptake, as well as undertake more research into new interventions for preventing STIs.”
Dr. Traeger reported no relevant financial disclosures.