Hepatitis A booster vaccine in children after infant immunization.
BACKGROUND
Hepatitis A vaccine provides long term protection against hepatitis A infection in adults and children older than 2 years of age. Few data are available regarding children younger than 2 years of age.


METHODS
Children who were vaccinated in infancy with hepatitis A vaccine were revaccinated at 4 years of age, and antibody titers were followed. Forty-four subjects who had been vaccinated with hepatitis A vaccine [Havrix, 360 enzyme-linked immunosorbent assay units (EU)] at the age of 2, 4 and 6 months were revaccinated with 720 EU of inactivated hepatitis A vaccine (Havrix) at 4 years of age.


RESULTS
Geometric mean titer (GMT) of 44 evaluable cases was 41 mIU/ml and 34 children (77.3%) were seropositive before the booster dose. Postvaccination blood samples were obtained from 37 cases. One month after booster dose GMT increased to 2884 mIU/ml, and all subjects were seropositive. Ten seronegative cases also seroconverted. The GMT of the seropositive cases showed anamnestic response after the booster dose (57 mIU/ml before booster dose, 5623 mIU/ml after the booster). No serious adverse event was seen after the booster dose.


CONCLUSIONS
We conclude that childhood hepatitis A virus revaccination after infant immunization is highly immunogenic and safe.
Infectious Disease, Department of Pediatrics, HacettepeUniversity School of Medicine, Ankara, Turkey. akara@gen.hun.edu.tr
Güler
G
Kanra
Sangül S
SS
Yalcin
Ates
A
Kara
Elif
E
Ozmert
Kadriye
K
Yurdakök
D000914:Antibodies, Viral / Q000097:blood; D002675:Child, Preschool; D006506:Hepatitis A / Q000517:prevention & control; D022362:Hepatitis A Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*; D030041:Hepatitis A virus / Q000276:immunology*; D006801:Humans; D017589:Immunization Programs; D007117:Immunization, Secondary; D007223:Infant; D013997:Time Factors
D000914:Antibodies, Viral; D022362:Hepatitis A Vaccines