title: Hepatitis B virus in the Lao People's Democratic Republic: a cross sectional serosurvey in different cohorts.
abstract: BACKGROUND
  Despite hepatitis B vaccination at birth and at 6, 10 and 14 weeks of age, hepatitis B virus (HBV) infection continues to be endemic in the Lao People's Democratic Republic (PDR). We carried out a cross-sectional serological study in infants, pre-school children, school pupils and pregnant women to determine their burden of disease, risk of infection and vaccination status.
  
  
  METHODS
  A total of 2471 participants between 9 months and 46 years old were recruited from urban (Vientiane Capital, Luang Prabang), semi-urban (Boulhikhamxai and Savannakhet) and remote rural areas (Huaphan). All sera were tested for anti-HBs and anti-HBc. Sera testing positive for anti-HBc alone were further tested for the presence of HBsAg.
  
  
  RESULTS
  A low prevalence of HBsAg (0.5%) was detected among infants from Vientiane and Luang Prabang, indicating some success of the vaccination policy. However, only 65.6% had protective anti-HBs antibodies, suggesting that vaccination coverage or responses remain sub-optimal, even in these urban populations.In pre-school children from remote areas in Huaphan, 21.2% were positive for anti-HBc antibodies, and 4.6% were for HBsAg positive, showing that a significant proportion of children in these rural regions have early exposure to HBV. In pre-school children with 3 documented HBV vaccinations, only 17.0% (15/55) were serologically protected.Among school-children from semi-urban regions of Luang Prabang, Boulhikhamxai and Savannakhet provinces, those below the age of 9 who were born after HBV vaccine introduction had anti-HBc and HBsAg prevalence of 11.7% and 4.1%, respectively. The prevalence increased to 19.4% and 7.8% of 10-14 year olds and to 27% and 10.2% of 15-19 year olds.Pregnant women from Luang Prabang and Vientiane had very high anti-HBc and HBsAg prevalence (49.5% and 8.2%), indicating high exposure and risk of onward vertical transmission to the unborn infant.
  
  
  CONCLUSIONS
  Overall, the results demonstrate a dramatic deficiency in vaccination coverage and vaccine responses and/or documentation within the regions of Lao PDR studied, which included urbanized areas with better health care access. Timely and effective hepatitis B vaccination coverage is needed in Lao PDR.
authors.forename: Antony P
authors.initials: AP
authors.lastname: Black
authors.forename: Phonethipsavanh
authors.initials: P
authors.lastname: Nouanthong
authors.forename: Naphavan
authors.initials: N
authors.lastname: Nanthavong
authors.forename: Chanthasone
authors.initials: C
authors.lastname: Souvannaso
authors.forename: Keooudomphone
authors.initials: K
authors.lastname: Vilivong
authors.forename: Prapan
authors.initials: P
authors.lastname: Jutavijittum
authors.forename: Bounthome
authors.initials: B
authors.lastname: Samountry
authors.forename: Nina
authors.initials: N
authors.lastname: Lütteke
authors.forename: Judith M
authors.initials: JM
authors.lastname: Hübschen
authors.forename: Sylvie
authors.initials: S
authors.lastname: Goossens
authors.forename: Fabrice
authors.initials: F
authors.lastname: Quet
authors.forename: Yves
authors.initials: Y
authors.lastname: Buisson
authors.affiliation: Lao-Lux Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR. Claude.Muller@crp-sante.lu.
authors.forename: Claude P
authors.initials: CP
authors.lastname: Muller
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006509:Hepatitis B / Q000097:blood / Q000453:epidemiology* / Q000517:prevention & control; D006510:Hepatitis B Antibodies / Q000097:blood*; D006512:Hepatitis B Core Antigens / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000097:blood*; D017325:Hepatitis B Vaccines / Q000627:therapeutic use; D006515:Hepatitis B virus; D006801:Humans; D007223:Infant; D018445:Infectious Disease Transmission, Vertical; D007812:Laos / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D015995:Prevalence; D012424:Rural Population; D014505:Urban Population; D014611:Vaccination; D055815:Young Adult
chemical_list: D006510:Hepatitis B Antibodies; D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines