The impact of HIV pre-exposure prophylaxis on sexually transmitted infections incidence in Bulgaria

BACKGROUND: The global introduction of effective Pre-Exposure Prophylaxis (PrEP) alongside with available antiretroviral medications against HIV strongly limited the spread of infection among the high-risk population. This remarkable success predisposes to riskier sexual behaviour and has emerged as leading cause of the increased incidence of sexually transmitted infections (STIs) in sizes of new threatening pandemic. METHODS: Checkpoint - Sofia is a medical centre located in Sofia, Bulgaria for consultations, prevention, diagnosis and treatment of STIs and HIV. Retrospective clinical study was performed on 507 consulted HIV-negative males with monitored normal renal function (October 2020 to March 2023). RESULTS: The mean age was 32±7.8 years (18-58 years) with prevalent ages <30 and 30-40 years (41% and 47%, respectively). As “men having sex with men” (MSM) identified themselves 96% of the studied individuals and 131 (26%) reported past STI history. Drug substances usage monthly reported 25% and weekly 11%; vaccinated for HBV <55%. On demand regimen (2 + 1+1 tablets) of PrEP was preferred at 91% and 15% switched to every-day receiving before increased risk. Voluntary were tested 58% of the subjects at least once during the first year of PrEP intake. No one was positive for HIV, HBV and HCV. We observed notable increase of STIs such as syphilis, chlamydia and gonorrhoea among the PrEP users - 9% (3/4 of them in the initial phase of the disease), 6% and 4%, respectively. Mixed infection (gonorrhoea and chlamydia) was confirmed at three. CONCLUSIONS: The drastic increase of unprotected sex practices in people regularly taking PrEP gradually leads to а significant raise of other STIs and potential antibiotic resistance. This trend confirms the extreme importance of sexual health centres in the application of parallel approach towards HIV/STIs including periodic screening among risk groups, confirmation of asymptomatic cases and conduction of proper prevention or therapy. KEY MESSAGES: • The dramatic increase of unprotected sex practices in people regularly taking PrEP as HIV prevention, gradually leads to a drastic raise of other STIs and potential antibiotic resistance. • Sexual health centres play a key role in the emergent screening among risk groups together with applying of preventive measures.