We appreciate the commentary  about our analysis and agree that preexposure prophylaxis (PrEP) for HIV is a critical strategy for the prevention of acquisition of HIV infection. The authors of the commentary  acknowledge the importance of our findings; however, they raise concerns that our findings might partially be explained by the overall general increase in incidence of sexually transmitted infections (STIs) among MSM since 2000 and the increased frequency of STIs testing among PrEP users. Furthermore, they raise concerns about the ability to replicate findings because of limited data availability and distortions made by an advocacy group using the findings to promote their own agenda.
Although we agree that a general increase in STIs over time and increased detection of STIs in PrEP cohorts might play some role in higher STI rates among PrEP users, multiple other recent studies have supported our results. Investigators in Boston reported that PrEP users had incident bacterial STIs 3.4 times more frequently than non-PrEP users in a retrospective age-adjusted multivariable analysis of health records at Fenway Health. Incident bacterial STIs occurred 1.4 times more frequently in their overall population every subsequent year from 2010 to 2015 . In addition, in a recent study conducted in San Francisco of mostly MSM who recently began PrEP, 41% reported decreased condom use and had high incidence of STIs with 30% of participants reporting at least one STI over the course of 6-month follow-up . Another study that included data from 2004 to 2014 also collected in San Francisco found that only 10% of PrEP users reported consistently using condoms compared with 25% of non-PrEP users . Finally, yet another study of PrEP use in MSM found that among their cohort 26% had early syphilis, gonorrhea, or chlamydia at baseline and 51% were diagnosed with an incident STI in the over 48 weeks of follow-up . Clearly, STIs are associated with and are frequent among PrEP users.
In terms of data availability for the Project Explore dataset, we requested data from one of the principal investigators and received access to the Atlas Scharp website: https://atlas.scharp.org/cpas/login/EXPLORE/Study%20Data/login.view?returnUrl=%2Fcpas%2Fstudy%2FEXPLORE%2FStudy%2520Data%2Fdataset.view%3FdatasetId%3D21. Prior publications have reported on STI incidence from the Project Explore dataset . We restricted our data analysis to the observation time in which STI testing was performed.
The authors of the commentary  conducted an additional analysis based on our reported table in the supplementary table for ‘any STI.’ We did not report an analysis of ‘any STI’ because of concerns of high variation in the frequency of testing for different STIs. The authors of the commentary  found a nearly three-fold higher STI incidence among PrEP users versus non-PrEP users.
We agree that one of the limitations of our analysis was the difference in frequency of STI testing between selected cohorts. We presented unadjusted data because adjustment might over or under control for the true incidence of select STIs among the cohorts. Lower rates of testing could bias results toward a higher relative risk.
The authors of the commentary  finally noted that an advocacy group used our analysis to promote the disadvantages and risks of PrEP for HIV. Although PrEP is an important strategy in the fight to eliminate HIV, it is also important to acknowledge that it is not the only, nor the best, strategy. To control sexually transmitted HIV, programs must promote regular HIV testing, access to HIV treatment, viral suppression, condom use, partner reduction, and, in some settings, male circumcision. Bacterial STIs that may be indirectly caused by use of PrEP should be considered by providers who must weigh the advantages and disadvantages of PrEP to ensure that the best personalized strategy is recommended to each patient [7,8]. Given that PrEP is indicated for at-risk individuals, risk reduction for other STIs should be offered in addition to PrEP as part of every comprehensive sexual health program.
Conflicts of interest
There are no conflicts of interest.
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