Introduction Pre-exposure prophylaxis (PrEP) prevents HIV infections but not other STIs. We assessed prevalence and incidence of STIs among PrEP users in the NSW demonstration study, PRELUDE.
Methods By 14 July 2015, 268 gay and homosexually-identified men (GHM) were enrolled and started taking PrEP; 98 (36.6%) and 27 (10.1%) had reached three and six-month follow-up respectively. STI testing was conducted at baseline and quarterly follow-up visits. We calculated the baseline prevalence and incidence of STIs. The sample STI incidence will be compared with the population incidence in NSW.
Results At enrolment, 17.2% of participants were diagnosed with ≥1 STI, including 10.8% with rectal gonorrhoea, rectal chlamydia and/or syphilis. The latter three STIs were diagnosed in 2.6%, 7.8%, and 1.1% of men, respectively. Among 98 men at 3-month follow-up, 17.3% were diagnosed with any of these STIs (3.1% had rectal gonorrhoea, 11.2% rectal chlamydia and 4.1% syphilis). At three months of follow-up, the incidence of these STIs was 18.4, 67.4 and 24.5 per 100 person-years (PY), respectively. By 14 July 2015, 27 PrEP users reached six months of follow-up. In this group, the incidence of rectal gonorrhoea was 29.6 per 100 PY (11.2% increase from month three follow-up, p < 0.04). No HIV infections were observed in the cohort.
Conclusion Among PrEP users in PRELUDE, the baseline prevalence and incidence of STIs were high and remained high in the early follow-up (indeed, the incidence of gonorrhoea has increased). Despite enrolment in a clinical study, with frequent follow-up, STI testing and treatment, PrEP users remain at very high risk of STIs. Longer follow-up is necessary to assess whether STI trends among PrEP users will change. The investigation of prophylaxis against other STIs and other methods of testing and treating STIs among these high-risk men appears to be warranted.
Disclosure of interest statement The PRELUDE study is funded by the NSW Ministry of Health, with Gilead Sciences providing the study medication (Truvada).