title: Duration of protection against hepatitis A for the current two-dose vaccine compared to a three-dose vaccine schedule in children.
abstract: BACKGROUND
  Hepatitis A is mostly a self-limiting disease but causes substantial economic burden. Consequently, United States Advisory Committee for Immunization Practices recommends inactivated hepatitis A vaccination for all children beginning at age 1 year and for high risk adults. The hepatitis A vaccine is highly effective but the duration of protection is unknown.
  
  
  METHODS
  We examined the proportion of children with protective hepatitis A antibody levels (anti-HAV ≥20 mIU/mL) as well as the geometric mean concentration (GMC) of anti-HAV in a cross sectional convenience sample of individuals aged 12-24 years, who had been vaccinated with a two-dose schedule in childhood, with the initial dose at least 5 years ago. We compared a subset of data from persons vaccinated with two-doses (720 EL.U.) at age 3-6 years with a demographically similar prospective cohort that received a three-dose (360 EL.U.) schedule and have been followed for 17 years.
  
  
  RESULTS
  No significant differences were observed when comparing GMC between the two cohorts at 10 (P=0.467), 12 (P=0.496), and 14 (P=0.175) years post-immunization. For the three-dose cohort, protective antibody levels remain for 17 years and have leveled-off over the past 7 years.
  
  
  CONCLUSIONS
  The two- and three-dose schedules provide similar protection >14 years after vaccination, indicating a booster dose is not needed at this time. Plateauing anti-HAV GMC levels suggest protective antibody levels may persist long-term.
authors.affiliation: Arctic Investigations Program, Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 4055 Tudor Centre Drive, Anchorage, AK 99508, USA. GRaczniak@cdc.gov
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Raczniak
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Thomas
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Bulkow
authors.forename: Susan E
authors.initials: SE
authors.lastname: Negus
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Zanis
authors.forename: Michael G
authors.initials: MG
authors.lastname: Bruce
authors.forename: Philip R
authors.initials: PR
authors.lastname: Spradling
authors.forename: Eyasu H
authors.initials: EH
authors.lastname: Teshale
authors.forename: Brian J
authors.initials: BJ
authors.lastname: McMahon
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006506:Hepatitis A / Q000276:immunology* / Q000517:prevention & control*; D035922:Hepatitis A Antibodies / Q000276:immunology; D022362:Hepatitis A Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D008297:Male; D011446:Prospective Studies; D013997:Time Factors; D014481:United States; D014611:Vaccination; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D055815:Young Adult
chemical_list: D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines; D015164:Vaccines, Inactivated