Observational study of vaccine efficacy 14 years after trial of hepatitis B vaccination in Gambian children.
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.
Whittle
Hilton
H
Medical Research Council Laboratories, PO Box 273, Banjul, Gambia. hwhittle@mrc.gm
Jaffar
Shabbar
S
Wansbrough
Michael
M
Mendy
Maimuna
M
Dumpis
Uga
U
Collinson
Andrew
A
Hall
Andrew
A
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
D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines