title: Effect of age and frequency of injections on immune response to hepatitis B vaccination in drug users.
abstract: Despite the high immunogenicity of the hepatitis B vaccine, evidence suggests that immunological response in drug users is impaired compared to the general population. A sample of not-in-treatment adult drug users from two communities in Houston, TX, USA, susceptible to hepatitis B virus (HBV), was sampled via outreach workers and referral methodology. Participants were randomized to either the standard multi-dose hepatitis B vaccine schedule (0, 1, and 6 months) or to an accelerated (0, 1, and 2 months) schedule. The participants were followed for 1 year. Antibody levels were measured at 2, 6 and 12 months after enrollment in order to determine the immune responses. At 12 months, cumulative adequate protective response was achieved in 65% of the HBV susceptible subgroup using both the standard and accelerated schedules. The standard group had a higher mean antibody titer (184.6 mIU/mL vs 57.6 mIU/mL). But at 6 months, seroconversion at the adequate protective response was reached by a higher proportion of participants and the mean antibody titer was also higher in the accelerated schedule group (104.8 mIU/mL vs. 64.3 mIU/mL). Multivariate analyses indicated a 63% increased risk of non-response for participants 40 years or older (p=0.046). Injecting drugs more than once a day was also highly associated with the risk of non-response (p=0.016). Conclusions from this research will guide the development of future vaccination programs that anticipate other prevalent chronic conditions, susceptibilities, and risk-taking behaviors of hard-to-reach populations.
authors.affiliation: Division of Epidemiology and Center for Infectious Diseases, The University of Texas Health Science Center at Houston, School of Public Health, 1200 Herman Pressler, Houston, TX 77030, USA.
authors.forename: Thanh Q
authors.initials: TQ
authors.lastname: Tran
authors.forename: Carolyn Z
authors.initials: CZ
authors.lastname: Grimes
authors.forename: Dejian
authors.initials: D
authors.lastname: Lai
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Troisi
authors.forename: Lu-Yu
authors.initials: LY
authors.lastname: Hwang
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D055030:Drug Users; D005260:Female; D006509:Hepatitis B / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood; D017325:Hepatitis B Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013781:Texas; D014611:Vaccination / Q000379:methods*; D055815:Young Adult
chemical_list: D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines
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