title: Observational study of vaccine efficacy 14 years after trial of hepatitis B vaccination in Gambian children.
abstract: OBJECTIVE
  To determine the duration of protection from hepatitis B vaccine given in infancy and early childhood.
  
  
  METHODS
  Cross sectional serological study of hepatitis B virus infection in children of various ages 14 years after the start of a trial of vaccination regimens.
  
  
  METHODS
  Two villages in the Gambia.
  
  
  METHODS
  Children and adolescents given hepatitis B vaccine in infancy or early childhood: 232 were aged 1-5 years, 225 aged 5-9 years, 220 aged 10-14 years, and 175 aged 15-19 years.
  
  
  METHODS
  Vaccine efficacy against infection and against chronic infection in the different age groups.
  
  
  RESULTS
  Vaccine efficacy against chronic carriage of hepatitis B virus was 94% (95% confidence interval 89% to 97%), which did not vary significantly between the age groups. Efficacy against infection was 80% (76% to 84%). This was significantly lower in the oldest age group (65%, 56 to 73). Of the uninfected participants in this age group, 36% had no detectable hepatitis B virus surface antibody. Time since vaccination and a low peak antibody response were the most powerful risk factors for breakthrough infection (P<0.001 in each case). Low peak antibody response was also a risk factor for chronic carriage (odds ratio 95, 19 to 466).
  
  
  CONCLUSIONS
  Children vaccinated in infancy are at increased risk of hepatitis B virus infection in the late teens. The risk of chronic carriage after sexual exposure needs further assessment to determine if booster vaccines are necessary.
authors.affiliation: Medical Research Council Laboratories, PO Box 273, Banjul, Gambia. hwhittle@mrc.gm
authors.forename: Hilton
authors.initials: H
authors.lastname: Whittle
authors.forename: Shabbar
authors.initials: S
authors.lastname: Jaffar
authors.forename: Michael
authors.initials: M
authors.lastname: Wansbrough
authors.forename: Maimuna
authors.initials: M
authors.lastname: Mendy
authors.forename: Uga
authors.initials: U
authors.lastname: Dumpis
authors.forename: Andrew
authors.initials: A
authors.lastname: Collinson
authors.forename: Andrew
authors.initials: A
authors.lastname: Hall
mesh_terms: D000293:Adolescent; D000328:Adult; D002353:Carrier State; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005714:Gambia / Q000453:epidemiology; D006512:Hepatitis B Core Antigens / Q000097:blood; D006514:Hepatitis B Surface Antigens / Q000097:blood; D017325:Hepatitis B Vaccines / Q000276:immunology*; D019694:Hepatitis B, Chronic / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D006801:Humans; D007223:Infant; D015995:Prevalence; D012044:Regression Analysis; D013997:Time Factors; D016896:Treatment Outcome; D014611:Vaccination
chemical_list: D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines