Immune Response of Hepatitis B Vaccine Booster Dose

One hundred and twenty-three children who had received no, incomplete and complete primary hepatitis B vaccination but had negative or very low anti-HBs titer were immunized with a single dose of recombinant hepatitis B vaccine. Blood tests for anti-HBs were obtained at 30 ± 5 days after the booster immunization. Twelve of 18 (66.7%) children without prior immunization (group 1) seroconverted following the single dose. Seroconversion rates in children who had undetectable anti-HBs with incomplete and complete primary immunization (group 2 and 3) were 83.34% and 94.5%, respectively. All children with complete 3dose vaccination but who had low anti-HBs titer (group 4) also seroconverted. This study confirmed that immunological memory, allowing a protective anamnestic response, lasted at least 8 years in children who had received primary HB immunization with undetectable anti-HBs. Therefore, we conclude that the booster dose after complete vaccination is not necessary in healthy children. Correspondence: Prof Yong Poovorawan, Viral Hepatitis Research Unit, Department of Pediatrics, Chulalongkorn University and Hospital, Rama IV Road, Bangkok 10330,