Past infection with hepatitis A virus among Vancouver street youth, injection drug users and men who have sex with men: implications for vaccination programs

Background: In Canada, inactivated hepatitis A vaccines are targeted select ively at those at increased risk for infection or its complications. In ord er to evaluate the need for routine hepatitis A vaccination programs in Van couver for street youth, injection drug users (IDUs) and men who have sex w ith men (MSM), we determined the prevalence of antibodies against hepatitis A virus (HAV) and risk factors for HAV in these groups. Methods: The frequency of past HAV infection was measured in a sample of Va ncouver street youth, IDUs and MSM attending outreach and STD clinics and n eedle exchange facilities by testing their saliva for anti-HAV immunoglobul in G. A self-administered, structured questionnaire was used to gather soci odemographic data. Stepwise logistic regression was used to evaluate the as sociation between presumed risk factors and groups and past HAV infection. Results: Of 494 study participants, 235 self-reported injection drug use, 5 1 were self-identified as MSM and 111 met street youth criteria. Positive t est results for anti-HAV were found in 6.3% of street youth (95% confidence interval [CI] 2.6%-12.6%), 42.6% (95% CI 36.2%-48.9%) of IDUs and 14.7% (9 5% CI 10.4%-19.1%) of individuals who denied injection drug use. Among men who denied injection drug use, the prevalence was 26.3% (10/38) for MSM and 12% (21/175) for heterosexuals. Logistic regression showed that past HAV i nfection was associated with increased age and birth in a country with high rates of hepatitis infection. Injection drug use among young adults (25-34 years old) was a significant risk factor for a positive anti-HAV test (p = 0.009). MSM were also at higher risk for past HAV infection, although this association was nominally significant (p = 0.07). Interpretation: Low rates of past HAV infection among Vancouver street yout h indicate a low rate of virus circulation in this population, which is vul nerable to hepatitis A outbreaks. An increased risk for HAV infection in ID Us and MSM supports the need to develop routine vaccination programs for th ese groups also.