title: Observational study of vaccine efficacy 24 years after the start of hepatitis B vaccination in two Gambian villages: no need for a booster dose.
abstract: OBJECTIVE
  To determine the duration of protection from hepatitis B vaccine given in infancy and early childhood and asses risk factors for HBV infection and chronic infection.
  
  
  METHODS
  In 1984 infant HBV vaccination was started in two Gambian villages. Cross sectional serological surveys have been undertaken every 4 years to determine vaccine efficacy. In the current survey 84.6% of 1508 eligible participants aged 1-28 years were tested. A spouse study was conducted in females (aged 14 years and above) and their male partners.
  
  
  RESULTS
  Vaccine efficacy against chronic infection with hepatitis B virus was 95.1% (95% confidence interval 91.5% to 97.1%), which did not vary significantly between age groups or village. Efficacy against infection was 85.4% (82.7% to 87.7%), falling significantly with age. Concentrations of hepatitis B antibody fell exponentially with age varying according to peak response: 20 years after vaccination only 17.8% (95% CI 10.1-25.6) of persons with a low peak response (10-99 mIU/ml) had detectable HBs antibody compared to 27% (21.9% to 32.2%) of those with a high peak response (>999 mIU/ml). Time since vaccination and a low peak response were the strongest risk factors for HBV infections; males were more susceptible, marriage was not a significant risk for females. Hepatitis B DNA was not detected after infection, which tested soley core antibody positive. An undetectable peak antibody response of <10 mIU/ml and a mother who was hepatitis B e antigen positive were powerful risk factors for chronic infection.
  
  
  CONCLUSIONS
  Adolescents and young adults vaccinated in infancy are at increased risk of hepatitis B infection, but not chronic infection. Married women were not at increased risk. There is no compelling evidence for the use of a booster dose of HBV vaccine in The Gambia.
authors.affiliation: Medical Research Council Laboratories, The Gambia, Banjul, the Gambia, West Africa. mendym@iarc.fr
authors.forename: Maimuna
authors.initials: M
authors.lastname: Mendy
authors.forename: Ingrid
authors.initials: I
authors.lastname: Peterson
authors.forename: Safayet
authors.initials: S
authors.lastname: Hossin
authors.forename: Tom
authors.initials: T
authors.lastname: Peto
authors.forename: Momodou L
authors.initials: ML
authors.lastname: Jobarteh
authors.forename: Adam
authors.initials: A
authors.lastname: Jeng-Barry
authors.forename: Mamadi
authors.initials: M
authors.lastname: Sidibeh
authors.forename: Abdoulie
authors.initials: A
authors.lastname: Jatta
authors.forename: Sophie E
authors.initials: SE
authors.lastname: Moore
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hall
authors.forename: Hilton
authors.initials: H
authors.lastname: Whittle
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005714:Gambia; D006509:Hepatitis B / Q000453:epidemiology / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood; D017325:Hepatitis B Vaccines / Q000627:therapeutic use*; D006801:Humans; D007117:Immunization, Secondary; D007223:Infant; D008297:Male; D055815:Young Adult
chemical_list: D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines