ABSTRACT
BACKGROUND: Immunization against hepatitis A and B has been available for some time, protecting against both infections. With a view to achieving further reduction in the number of interventions and increasing convenience of the vaccinee, we investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine in healthy 4- to 20-year-old subjects at a 0, 6-month schedule. METHODS: Two hundred forty-eight study subjects were allocated to two study groups and received either two doses of the combined hepatitis A and B vaccine (68% of subjects) or the corresponding monovalent hepatitis A and hepatitis B vaccines (32% of subjects) concomitantly in opposite arms. Reactogenicity was assessed via diary cards after each vaccination. Serum samples were analyzed at months 1, 2, 6, and 7. RESULTS: All vaccines were well tolerated and very few symptoms were scored as severe. All but one subject seroconverted for anti-hepatitis A virus (anti-HAV) antibodies (98.6%) and 100% of subjects seroconverted for anti-hepatitis B (HBs) antibodies, with respective seroprotection rates of 98.7% for the combined vaccine group and 95.9% for the concomitant vaccine group (p >0.05), respectively. Geometric mean titers were higher in the group receiving the combined vaccine: 6,635 mIU/mL vs. 2,728 mIU/mL (p = 0.0001) for anti-HAV and 3,362 mIU/mL vs. 1,724 mIU/mL (p = 0.0205) for anti-HBs, respectively. Younger subjects had a stronger immune response compared to older subjects. CONCLUSIONS: The combined hepatitis A and B vaccine was well tolerated at this two-dose schedule. The combined vaccine had higher immunogenicity, probably explained by a adjuvant effect of the antigens. Vaccination programs requiring fewer injections will most likely have a positive impact on compliance rate and comfort of the vaccinee.
