Prospective screening for monkeypox infection among men who have sex with men at an infectious diseases outpatient clinic in Copenhagen, Denmark

Since 2022, over 102,000 cases of mpox clade IIb have been reported worldwide, primarily among men who have sex with men. Key risk factors include human immunodeficiency virus (HIV) infection and the use of HIV pre-exposure prophylaxis (PrEP). In Denmark, the pox vaccine (Imvanex®) has been available to at-risk individuals since 2022. However, emerging cases of mpox reinfection have raised concerns regarding vaccine-induced immunity and the potential for asymptomatic transmission. This study aimed to assess the necessity of screening for mpox in an asymptomatic yet high-risk population, the majority of whom had been vaccinated. Between August and October 2023, we screened 123 PrEP users for mpox at the outpatient clinic of Copenhagen University Hospital – Amager and Hvidovre, Denmark. Polymerase chain reaction testing for mpox was conducted using rectal swabs. Among the participants, 97 had received at least one dose of the mpox vaccine. No mpox cases were detected. These findings suggest that in a highly vaccinated, high-risk population during a period of very low mpox prevalence in Denmark, asymptomatic mpox circulation is unlikely. The results support the current public health strategy of prioritizing mpox testing for symptomatic individuals and implementing contact tracing during low-prevalence periods with high vaccine coverage.