Pre exposure prophylaxis (PrEP) and sexually transmitted diseases (STIs).

The Pre-exposure Prophylaxis Prophylaxis Expanded (PrEPX)
study is a multisite, open label intervention study in Victoria,
Australia. The study includes 2,892 gay and bisexual men who
were followed for a total of 3,185 person years. The incidence of
chlamydia, gonorrhea and syphilis was followed after receipt
of PrEP. Incidence of STIs in 1,378 patients who had preenrollment
data available increased from 69.5 per 100 person-years
prior to enrollment to 98.4 after initiation of PrEP.

Ref; Traeger et al. JAMA 2019:321:1380-1390

Comment: It seems very likely that there is a causal relationship
between the widespread usage of PrEP and the increase in
STIs. Intensified testing and treatment may curb the rapid increase
in STIs that have been observed in several studies.