Those who are homeless have a higher chance of getting hepatitis B virus (HBV). Throughout the United States there is an average of 2.9 out of 100,000 cases of HBV. A study made up of those who are homeless and have a mental illness or use substances found 32.5% tested positive for HBV. Hepatitis B can be prevented through a course of 3 doses of a vaccine. These must be administered at intervals within a 6 month period. The period and number of doses makes it difficult to complete successfully for those experiencing homelessness.

Completion and Subject Loss within an Intensive Hepatitis Vaccination Intervention among Homeless Adults: The Role of Risk Factors, Demographics, and Psychosocial Variables was published in Health Psychology, 29(3), 317 in 2010.