The Hepatitis B Vaccine Booster Response Among the Youth Who Had Completed Neonatal Hepatitis B Vaccines

This cohort study was conducted between October 2007 and Jan 2009. The target population was subjects aged 18-23 years who were born after 1984 when the Taiwanese national HB vaccination program was launched. Their vaccination records must have shown a completed neonatal HB vaccination, and they were seronegative for all three HB viral markers including HBsAg(Hepatitis B surface antigen), anti-HBc(core antibody against Hepatitis B), and anti-HBs(Surface antibody against Hepatitis B) within 2 years of entry into the study and at study entry. They were recruited through a Student's Health Center Clinic referral, Bulletin Board System posts, and Web-broadcast invitation. The neonatal HB vaccination records were verified through linkage to the Taiwan Center for Disease Control databank. Signed informed consent was obtained from all the participants and their parents or guardians. Pregnant females, persons with a previous history of allergy to HB vaccines, or allergy to yeast were excluded. First 3 months are screen phase to recruit college students for assay of hepatitis B viral markers. Seronegative subjects were approached for enrollment into receiving hepatitis B vaccine booster afterwards. All participants were tested for HB markers at enrollment, even if they had been tested in the previous months, to confirm their status. A questionnaire was completed at enrolment to record sociodemographic factors including age, gender, self reported family history of hepatitis B carriers, self reported blood type, and so on. The participants then received three intramuscular doses of HB vaccine (Engerix-B, recombinant hepatitis B surface antigen, 20 microgram/ml/vial, GlaxoSmithKline, Belgium) at baseline and at the 1st and 6th month follow-up visits. Their anti-HBs status was checked at baseline, 7-10 days, 1 month, 6 months, and 7 months following the first dose of HB vaccine. Adverse effects associated with the vaccine were also reported within one week after each Engerix-B injection.