Background Hepatitis C virus (HCV) is an increasing health issue among key populations such as men who have sex with men (MSM). We sought to assess the burden of and risk factors for HCV among MSM in Vietnam.

Methods We analysed behavioural and demographic data and stored specimens from MSM surveyed in four provinces through Vietnam's 2009–2010 Integrated Biologic and Behavioural Survey, which used probability-based, respondent-driven sampling. Commercial hepatitis B surface antigen (HBsAg) and HCV/antibody (HCV Ag/Ab) testing were performed on archived sera with follow-up PCR for HCV RNA and genotype determination.

Results Among the 1588 MSM surveyed, the median (range) frequency, by province, of HCV Ag/Ab detection was 28.4% (13.7%–38.8%); 84.5% (83.1%–100%) among HIV-infected and 21.9% (8.9%–28.2%) among HIV-uninfected. HCV prevalence was higher in northern Hanoi and Hai Phong provinces than in southern Ho Chi Minh City and Chan Tho provinces. Among a convenience sample of 67 HCV Ag/Ab+ MSM, 67.2% were HCV RNA+; of 41 genotyped, 73.2% were genotype 1. HBsAg prevalence varied from 8.5% to 27.4%. In the multivariable logistic regression analysis, being HIV-infected (adjusted OR (aOR) 19.0; 7.0–51.9), ever having used injected drugs (aOR 4.4; 1.6–12.4) and age >25 years were significant risk factors for testing HCV Ag/Ab+.

Conclusions HCV infection in Vietnam appears to be high among MSM, particularly among HIV-infected MSM, with a north–south gradient. Given overlapping risk behaviours and associations between HCV and HIV, integrating HIV and HCV programme services to prevent both HIV and HCV transmission among MSM is indicated.