Rates of new sexually transmitted infections (STIs) are much higher among men who have sex with men (MSM) taking Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis (PrEP) than among other MSM. More research is needed, however, to determine whether starting PrEP leads to higher STI rates among MSM.
Publishing their findings in the journal AIDS, researchers conducted a meta-analysis of 18 studies of MSM in which new STI diagnoses were reported. Five of the studies included MSM given PrEP, and 14 were conducted with MSM who were not given PrEP. (One study, the PROUD study, included both a group given PrEP immediately and a group given PrEP on a deferred basis and thus fell into both the PrEP and the non-PrEP categories of studies.)
The participants of the 18 studies were followed for a cumulative 70,000 years.
The researchers found that the rates of new diagnoses of STIs among MSM given PrEP were 25.3 times greater for gonorrhea, 11.2 times greater for chlamydia and 44.6 times greater for syphilis, compared with the rates among MSM not given PrEP. After repeating the analysis but excluding studies conducted before 1999, the researchers found that the results were similar.
Looking to parse apart the contributing factors to the higher rate of STI diagnoses among MSM given PrEP, the meta-analysis’s authors theorized that the regular STI testing that is part of taking PrEP might have led to a higher rate of STI detection. A greater number of sex partners and a higher rate of condomless sex among those given PrEP might also have contributed to their higher STI diagnosis rate.
The study is limited by the fact that, except in the case of PROUD, the researchers compared different populations of MSM from study to study. They also compared groups that tested for STIs at different frequencies and used different variations of STI tests. Additionally, the PrEP studies specifically sought out participants engaging in high-risk sexual behaviors, while the other studies might have had different criteria with regard to sexual risk taking. However, participants in many of the non-PrEP studies were indeed recruited based on some level of reported sexual risk taking.
The researchers joined with others who have called upon the Centers for Disease Control and Prevention (CDC) to revise its PrEP guidelines to recommend that MSM using PrEP receive quarterly STI screenings, instead of the currently recommended semiannual screenings.
“Furthermore,” the authors wrote, “physicians must not only vigilantly identify patients that may benefit from PrEP but also provide their patients with a sexual health prevention package that includes quarterly STI screenings, timely treatment of infection, expedited partner treatment, and rescreening if positive. In addition, our results and prior reports, which not only found a higher incidence of STI among PrEP users versus nonusers but also high rates of condomless anal sex among PrEP users, suggest that more research is needed to understand if PrEP causes a higher incidence of STIs among MSM. We must ensure that our efforts fighting one public health crisis do not lead to another.”
To read the study abstract, click here.