Whether and how MSM modify sexual behaviors after initiating PrEP has not been well studied in non-research settings and is of particular importance as PrEP becomes more widely used.
We measured changes in sexual behavior among MSM attending an STD clinic in Seattle, WA who initiated PrEP. Sexual behavior during prior 30 days was reported in a computer-assisted self-interview (CASI) administered at PrEP initiation and subsequent clinic visits every 3 months. Bacterial sexually transmitted infections (STI) diagnosed during the periods before and after PrEP initiation were identified via STI surveillance records. MSM were asked about number of sexual partners, sexual positioning, and condom use with HIV-positive, HIV-negative, and unknown-status partners during the prior 30 days. We used linear regression to assess significance of behavioral trends. We describe the proportion of MSM reporting each behavior at each visit. We present the proportion of MSM diagnosed with chlamydia (CT), gonorrhea (GC), or syphilis in the 12 months prior to baseline for MSM who completed a baseline CASI, and the proportion of MSM diagnosed with CT, GC, or syphilis while taking PrEP, for those who completed at least one follow-up CASI.
220 men began PrEP during Sept 2014 – June 2016, and completed the behavioral section of the baseline CASI. Mean age of participants was 31 (SD: 8.5), and 63% were white. Mean number of sex partners and proportion of sex with each type of partner was stable during the study period (Table). The proportion of men reporting never using condoms for any anal sex or never using condoms during receptive anal intercourse with HIV-positive partners increased over the study period, but there were no clear trends with other position and partner serostatus combinations. 24% of men were diagnosed with GC, 17% with CT, and 19% with syphilis at baseline or during the 12-months prior to PrEP initiation. Among men with at least one follow-up visit (n=76; average follow-up time = 8.6 months), 34% were diagnosed with GC, 37% with CT, and 9% with syphilis while on PrEP.
MSM in our clinic reported decreased condom use during receptive anal intercourse with HIV-seropositive partners after initiating PrEP. The proportion of men diagnosed with CT and GC was higher in the time period after PrEP initiation, which could reflect increased risk behavior, increased detection during routine screening, or temporal increases in STD risk in the population.