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Hepatitis A booster vaccine in children after infant immunization
Güler Kanra1, Sangül S Yalcin, Ates Kara
1Infectious Disease, Department of Pediatrics, HacettepeUniversity School of Medicine, Ankara, Turkey. akara@gen.hun.edu.tr
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.
Conclusion:
We conclude that childhood hepatitis A virus revaccination after infant immunization is highly immunogenic and safe.