title: Comparison of the immune response of four different dosages of a yeast-recombinant hepatitis B vaccine in Singapore children: a four-year follow-up study.
abstract: The immunogenicity of four different dosages of yeast-derived hepatitis B vaccine (Merck, Sharp & Dohme: 0.6 micrograms, 1.25 micrograms, 2.5 micrograms and 5.0 micrograms), administered at 0, 1 and 6 months (0-1-6 schedule) intramuscularly, was evaluated in 122 seronegative healthy children 1-12 years of age. Three months after the first dose, 83.9-100% of the vaccinees seroconverted. Peak geometric mean titres (GMT) of between 1088 mlU/ml and 1699 mlU/ml were attained 3 months after completion of the vaccination schedule. After 24 months, anti-HBs (antibody to hepatitis B surface antigen) was detected in 93.1-100% of the vaccinees, but the GMT dropped to between 214.3 mlU/ml and 303.5 mlU/ml. After 48 months, 88.8-100% of the vaccinees continued to possess anti-HBs and 70.3-87% had titres above 10 mlU/ml. As expected, the GMT declined further to between 72.6 mlU/ml and 118.8 mlU/ml. There were no significant differences in seroconversion rates and GMT among the different dosage groups. All the vaccinees remained asymptomatic and free from hepatitis B virus infection. The study showed that reduced dosages of the vaccine (0.6 micrograms, 1.25 micrograms and 2.5 micrograms) were as immunogenic as the standard dose (5 micrograms); the 2.5-micrograms dose was recommended for the national childhood immunization programme in Singapore. No booster is necessary for at least four years after vaccination.
authors.affiliation: Quarantine & Epidemiology Department, Ministry of the Environment, Singapore.
authors.forename: K T
authors.initials: KT
authors.lastname: Goh
authors.forename: K L
authors.initials: KL
authors.lastname: Tan
authors.forename: K H
authors.initials: KH
authors.lastname: Kong
authors.forename: C J
authors.initials: CJ
authors.lastname: Oon
authors.forename: S H
authors.initials: SH
authors.lastname: Chan
mesh_terms: D000917:Antibody Formation; D002648:Child; D002675:Child, Preschool; D005500:Follow-Up Studies; D006509:Hepatitis B / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D006512:Hepatitis B Core Antigens / Q000097:blood / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000097:blood / Q000276:immunology; D006801:Humans; D007223:Infant; D016036:Seroepidemiologic Studies; D012846:Singapore / Q000453:epidemiology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use*; D014761:Viral Hepatitis Vaccines / Q000008:administration & dosage / Q000276:immunology / Q000627:therapeutic use*; D015003:Yeasts
chemical_list: D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens; D014614:Vaccines, Synthetic; D014761:Viral Hepatitis Vaccines