title: Vaccination against hepatitis B virus among people who inject drugs - A 20year experience from a Swedish needle exchange program.
abstract: People who inject drugs (PWID) are at particular risk of hepatitis B virus (HBV) acquisition, but often have poor access or adherence to HBV vaccination. Vaccination against HBV has been offered at a major Swedish needle exchange program (NEP) since 1994. The aim of this study was to evaluate vaccine completion and response rates, and the effect of sequential booster doses to non-responders to the standard vaccination schedule.
  
  
  
  PWID enrolled in the NEP 1994-2013, without serological markers for HBV at baseline (negative for HBsAg/anti-HBc/anti-HBs), were offered a three-dose standard intramuscular vaccination schedule (Engerix®-B, GSK, 20μg/mL, intended to be received at months 0, 1 and 6). Vaccination response was defined as protective levels of anti-HBs (⩾10mIU/mL). Up to three booster doses were then offered for non-responders, each followed by anti-HBs testing.
  
  
  
  HBV data was available for 2352 identifiable individuals at NEP enrolment, of whom 1516 (64.5%) had no markers for previous HBV exposure or vaccination. Vaccination was initiated for 1142 (75.3%) individuals and 898 (59.2%) completed the standard vaccination schedule. Post-vaccination anti-HBs levels were available from 800 individuals, with 598 (74.8%) responding to the basic vaccination schedule. After up to three booster doses a total of 676 (84.5%) individuals achieved protective anti-HBs levels. Non-response to vaccination was associated with higher age and anti-HCV positivity (p<0.001). Eighteen incident cases of HBV infection were observed among vaccine non-responders, as well as 30 cases among those who had not completed vaccination.
  
  
  
  We demonstrate the feasibility of including HBV vaccination in the services offered by a NEP, with completion of vaccination in a majority of HBV-susceptible PWID. The response to HBV vaccination among PWID was relatively low; however, the addition of up to three booster doses improved the response rate from 74.8 to 84.5%.
authors.affiliation: Department of Clinical Sciences, Infectious Disease Research Unit, Lund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Alanko Blomé
authors.affiliation: Department of Clinical Sciences, Infectious Disease Research Unit, Lund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Björkman
authors.affiliation: Department of Clinical Sciences, Infectious Disease Research Unit, Lund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Flamholc
authors.affiliation: Research and Development Center Skåne, Skåne University Hospital, Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Jacobsson
authors.affiliation: Department of Medical Microbiology, Lund University, Skåne University Hospital, Malmö, Sweden; Department of Translational Medicine, Clinical Virology, Lund University, Lund, Sweden. Electronic address: anders.widell@med.lu.se.
authors.forename: A
authors.initials: A
authors.lastname: Widell
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006509:Hepatitis B / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood; D017325:Hepatitis B Vaccines / Q000008:administration & dosage*; D006801:Humans; D007115:Immunization Schedule; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D018671:Needle-Exchange Programs; D012189:Retrospective Studies; D015819:Substance Abuse, Intravenous / Q000150:complications*; D013548:Sweden; D055815:Young Adult
chemical_list: C075654:Engerix-B; D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines
keywords: Hepatitis B; NEP; Needle exchange program; PWID; People who inject drugs; Vaccination