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.
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.
Authors: Noele P Nelson; Mark K Weng; Megan G Hofmeister; Kelly L Moore; Mona Doshani; Saleem Kamili; Alaya Koneru; Penina Haber; Liesl Hagan; José R Romero; Sarah Schillie; Aaron M Harris Journal: MMWR Recomm Rep Date: 2020-07-03