MEXICO CITY — A survey of young gay and bisexual men and transgender women in Chicago, a portion of whom were on pre-exposure prophylaxis (PrEP), has found no direct relationship between starting PrEP and any increase in subsequent sexually transmitted infections (STIs).
AIDSmap reported that the survey did find that people had more condomless sex, but it did not lead to more STIs.
Ethan Morgan of Chicago’s Northwestern University and Center for AIDS Research told the 10th International AIDS Society Conference in HIV Science (IAS 2019) is Mexico City that data were collected as part of RADAR, a cohort study of young men who have sex with men and transgender women aged between 16 and 29.
A total of 744 young people who attended six or more study visits were followed out of a total cohort of 1100. During the study period, a third of participants started PrEP (32.9%). (The fact that this was only 21% in the pre-conference abstract submitted a few months ago shows evidence of a rapid expansion in PrEP use.) About a third were also diagnosed with a rectal STI: 17% with rectal gonorrhoea and 23% with rectal chlamydia (some with both).
The study looked longitudinally at participants’ PrEP starts and STI diagnoses and asked the question: if participants started PrEP at one study visit, was it associated with a higher rate of STI diagnoses in the next two study visits? The answer was no.
Although there was no statistically significant association either way, the highest rectal STI diagnosis rate was in fact observed in people before they stated PrEP.
The rates of any rectal STI in the three visits prior to stating PrEP, in the third of people who did, varied from 16 to 25% depending on which study period they were diagnosed in. In contrast the rates of rectal STIs in the same study visits in people who had already started PrEP ranged for 9 to 16%. These were similar to STI rates in people who never started PrEP (11 to 13%) and in people who used PrEP intermittently or irregularly (15% for any study period).
AIDSmap reported that later studies will look at why more condomless sex did not lead to more STIs and whether this was due to higher testing and diagnosis rates or to a reduction in other sexual risks.