Participants taking tenofovir/emtricitabine (Truvada) for pre-exposure prophylaxis (PrEP) continued to have high rates of sexually transmitted infections (STIs) in two US PrEP demonstration projects, according to a pair of reports at the Conference on Retroviruses and Opportunistic Infections (CROI 2016) last month in Boston. Semi-annual STI testing missed many cases, leading researchers to suggest that gay men on PrEP could benefit from screening every three months.
One of the most common concerns surrounding PrEP is the high rate of STIs seen among users. There is little evidence that PrEP actually causes an increase in STIs, but gay and bisexual men at risk for HIV already have high STI rates, and many PrEP users are likely to be already having, or wish to have, sex without condoms.
As Sheena McCormack, lead investigator for the English PROUD study, explained at a CROI symposium on innovations in PrEP, “the pre-existing trajectory of rising STIs [among men who have sex with men] is carrying on, but PrEP means HIV doesn’t have to rise too.”
On the other hand, the regular STI screening recommended for people on PrEP encourages prompt diagnosis and treatment, which reduces onward transmission and could potentially contribute to lowering STI rates among PrEP users compared to non-users.