Scaling up testing for hepatitis C virus (HCV) among HIV-negative men who have sex with men (MSM) who are taking pre-exposure prophylaxis (PrEP), as well as HIV-positive men, could greatly reduce the emergent epidemic of sexually transmitted HCV among gay and bisexual men.
Initially, as this epidemic surfaced around 2000, the new HCV cases were predominantly seen among HIV-positive gay and bi men. More recently, signs have indicated that HIV-negative MSM are also at risk.
Publishing their findings in EclinicalMedicine, a research team led by Louis Macgregor, PhD, of the University of Bristol in the United Kingdom, devised a mathematical model to predict the effects of scaling up HCV testing among MSM in the United Kingdom.
The model presumed that in 2018, 4.7% of MSM were living with HIV and that 9.9% of those men were coinfected with HCV. The model also presumed that 1.2% of HIV-negative MSM had HCV and that 12.5% of HIV-negative MSM were on PrEP.
The model projected the HCV rate in 2030, measuring the outcomes against the World Health Organization’s target of reducing the rate of new annual transmissions of the virus, known as incidence, by 90% by that year.
Screening for HCV and treating the virus with direct-acting antivirals within six months of diagnosis among PrEP users would reduce incidence of the virus among all MSM by 67% if testing were conducted every 12 months and by 70% if testing were conducted every six months. Screening HIV-diagnosed individuals at the same frequencies would reduce HCV incidence among MSM by a respective 75% and 79%.
If MSM going on PrEP subsequently were to reduce their condom use by 50%, a phenomenon known as risk compensation, this would reduce the impact of HCV testing and treatment among MSM with HIV or on PrEP by less than 10%.
To reduce HCV incidence among MSM by 90% by 2030, presuming there was no risk compensation among those on PrEP and that both HIV-diagnosed MSM and those on PrEP were screened every six months, HIV-negative MSM not taking PrEP would also need to be screened, at an interval of every 5.6 months. The testing interval for HIV-negative men not using PrEP would need to narrow to every 4.4 months if MSM on PrEP were to engage in risk compensation.
If 25% of MSM took PrEP, the 2030 HCV elimination target could be reached without screening HIV-negative MSM not taking PrEP, regardless of whether the PrEP takers were to reduce their condom use by 50%.
To read the study, click here.