Background:  Recent data indicate that the prevalence of primary sexually transmitted hepatitis C virus (HCV) infection is stabilizing at 15% among HIV⁺ men who have sex with men (MSM) visiting our sexually transmitted infections (STI) clinic. This may suggest that incidence of primary infection is decreasing. However, little is known about the incidence of HCV reinfection in previously infected MSM. Our objective was to study the incidence rate of reinfection in HIV⁺ MSM who were HCV RNA^– at end of primary HCV treatment.

Methods:  Our study population comprised HIV⁺ MSM previously diagnosed with a sexually transmitted acute HCV infection at a HIV-outpatient clinic in Amsterdam, who were HCV RNA^– at end of treatment. Since most relapses occur within 2 months after treatment, we defined HCV reinfection as having an HCV RNA⁺ test result after having had a negative result at least 2 months after the end of treatment, and showing an HCV geno- or strain-type switch.  Backward HCV RNA testing on samples was performed to precisely estimate reinfection date. Person-years at risk were calculated from the date of the HCV^– sample 2 months after the end of treatment until the date of first reinfection (midpoint between last negative and first positive sample) or last negative sample.

Results:  During primary acute HCV treatment, 28 persons became HCV RNA^– and remained so until at last 2 months after the end of treatment. Within 2 months of treatment end, 2 of the 28 relapsed and were omitted from analysis. According to our definition, 6 persons had a reinfection:  1 person became positive 4 months after start follow-up, but his genotype was unknown and we therefore excluded him from analysis. Total follow-up time of the 25 persons was 35.5 years; median follow-up 1.1 years (IQR 0.4 to 1.9). Median time between test intervals was 2.9 months (IQR 1.6 to 4.1). The incidence of HCV reinfection in this group was 16.9 /100 person-years (95%CI 6.9 to 35.2).

Conclusions:  Despite high clearance rates and a possible decrease in incidence of primary HCV infection among HIV⁺ MSM in Amsterdam, an alarmingly high incidence of HCV reinfection was found in this group. The rate was about 10 times the HCV incidence described in HIV⁺ men without a history of HCV infection and should be further studied. This high reinfection rate indicates that prevention measures should be discussed and regular HCV testing should be continued after successful treatment.