Hepatitis A Seroprevalence and Risk Factors Among Homeless Adults in San Francisco: Should Homelessness Be Included in the Risk-Based Strategy for Vaccination?

Objectives. Homeless adults have an increased risk of infectious diseases due to sexual and drug-related behaviors and substandard living conditions. We investigated the prevalence and risk factors for presence of hepatitis A virus (HAV) antibodies among homeless and marginally housed adults. Methods. We analyzed serologic and questionnaire data from a study of marginally housed and homeless adults in San Francisco from April 1999 to March 2000. We tested seroprevalance for total antibodies to HAV (anti-HAV) and analyzed data using Chi-square tests and logistic regression. Results. Of the 1,138 adults in the study, 52% were anti-HAV positive. The anti-HAV prevalence in this study population was 58% higher than the expected prevalence based on age-specific prevalence rates from the general population. Number of years of homelessness (<= 1, 2-4, and; >= 5 years) was associated with anti-HAV prevalence (46%, 50%, and 61%, respectively, p<0.001). We found other differences in anti-HAV prevalence (p<0.05) for ever having injected drugs (63% vs. 42% for non-injectors), being foreign-born (75% vs. 51% among U.S.-born), race/ethnicity (72%, 53%, and 45% for Hispanic, white, and black people, respectively), and increasing age (38%, 49%, and 62% among those aged <35, 35-45, and >45 years, respectively). These variables all remained significant in a multivariate model. Conclusions. We found overall anti-HAV prevalence elevated in this San Francisco homeless population compared with the general U.S. population. These data show that anti-HAV was associated with homelessness independent of other known risk factors, such as being foreign-born, race/ethnicity, and injection drug use. This increase indicates an excess risk of HAV infection and the potential need to offer hepatitis A vaccination as part of homeless services.