Impact of HCV Testing and Treatment on HCV Transmission Among Men Who Have Sex With Men and Who Inject Drugs in San Francisco: A Modelling Analysis.

Background: Men who have sex with men who ever injected drugs (ever MSM-IDU) carry a high hepatitis C virus (HCV) burden. We estimated whether current HCV testing and treatment in San Francisco can achieve the 2030 World Health Organization (WHO) HCV elimination target on HCV incidence among ever MSM-IDU.

Methods: A dynamic HCV/HIV transmission model among MSM was calibrated to San Francisco data, including HCV antibody (15.5%, 2011) and HIV prevalence (32.8%, 2017) among ever MSM-IDU. MSM had high HCV testing (79%-86% ever tested, 2011-2019) and diagnosed MSM had high HCV treatment (65% ever treated, 2018). Following coronavirus disease 2019 (COVID-19)-related lockdowns, HCV testing and treatment decreased by 59%.

Results: Among all MSM, 43% of incident HCV infections in 2022 were IDU-related. Among ever MSM-IDU in 2015, HCV incidence was 1.2/100 person-years (95% credibility interval [CrI], 0.8-1.6). Assuming COVID-19-related declines in HCV testing/treatment persist until 2030, HCV incidence among ever MSM-IDU will decrease by 84.9% (95% CrI, 72.3%-90.8%) over 2015-2030. This decline is largely attributed to HCV testing and treatment (75.8%; 95% CrI, 66.7%-89.5%). Slightly greater decreases in HCV incidence (94%-95%) are projected if COVID-19 disruptions recover by 2025 or 2022.

Conclusions: We estimate that HCV incidence will decline by >80% over 2015-2030 among ever MSM-IDU in San Francisco, achieving the WHO target.