Sexual behaviour and STIs among MSM living with HIV in the PrEP era: the French ANRS PRIMO cohort study

In a context of declining condom use and high sexually transmitted infection (STI) incidence, the diffusion of "treatment as prevention" (Tasp) and more recently pre-exposure prophylaxis (PrEP) may have changed the sexual behaviour of newly diagnosed men who have sex with men (MSM) with HIV.

Six hundred and nine MSM were enrolled and followed annually between 2014 and 2021 in the ANRS PRIMO Cohort (ClinicalTrials.gov:NCT03148964) from the time of HIV seroconversion. We studied changes over calendar time in sexual behaviour before and after HIV diagnosis. Factors associated with inconsistent condom use (ICU) after HIV diagnosis, PrEP use by partner(s) and bacterial STI acquisition were studied in random-effects models.

In the 6 months preceding HIV diagnosis, the number of sexual partners decreased from a median of 10 (IQR: 4-19) in 2014 to 6 (3-11) in 2021. After HIV diagnosis, ICU increased from 57.1% (16/28) of visits in 2014 up to 84.2% (229/272) in 2020-2021. Up to 25% (63/229) of MSM with HIV in recent years reported the use of PrEP by their partner(s) as the reason for ICU; these MSM were less frequently in a stable relationship, had a higher number of sexual partners and higher education level than those who did not report the use of PrEP by their partner(s). STI incidence after HIV diagnosis increased between 2014 and 2016 and remained high afterwards. STI risk was no longer associated with PrEP use by partners after adjustment for the number of partners and calendar period. ICU, age below 35 years, not being in a stable relationship, higher number of sexual partners were independently associated with an increased risk of STI.

Implementation of TasP and more recently PrEP has led to major changes in the sexual behaviour of MSM with HIV. ICU has become overwhelmingly prevalent, PrEP use by the partner increasingly being the reported reason for ICU, behind TasP, which remains the main reason. Characteristics of MSM at the time of diagnosis of HIV have changed, with fewer number of sexual partners today than in 2014, which must lead to broaden the indications for PrEP prescription. STIs incidence remains high in MSM with HIV and requires improvements in screening and prevention methods such as pre- or post-exposition antibiotics or vaccines.