A two dose schedule for combined hepatitis A and hepatitis B vaccination in children ages one to eleven years.

ABSTRACT

RATIONALE A combined hepatitis A and B vaccine, Twinrix, containing at least 720 enzyme-linked immunosorbent assay units of hepatitis A antigen and 20 microg of hepatitis B antigen in the adult formulation and half those doses in the pediatric formulation, has been available in many countries since 1997. This vaccine is administered on a three dose schedule 0, 1 and 6 months. A reduction in the number of doses would add convenience for the vaccinees and reduce administration-associated costs. We investigated the safety and immunogenicity profile of the adult formulation administered at 0 and 6 months in children ages 1 to 11 years. METHODS: A total of 237 children of both sexes were enrolled. Blood sampling was performed at 0 and 1, 2, 6 and 7 months. Seropositivity for anti-hepatitis A virus was defined as > or = 33 mIU/ml and seroprotection against hepatitis B virus as > or =10 mIU/ml. Data on solicited and unsolicited adverse events were collected on diary cards. RESULTS: The vaccine was well-tolerated in all subjects. At Month 7 all subjects had seroconverted for anti-hepatitis A virus antibodies with a high geometric mean concentration (11 543 mIU/ml). We observed a continuous increase in anti-hepatitis B surface antibody (anti-HBs) seroconversion rates and seroprotection rates until Month 6. After the second dose (Month 7), all subjects seroconverted for anti-HBs antibodies with a high geometric mean concentration (8056 mIU/ml) and 98.5% of the subjects were considered seroprotected. CONCLUSION: The two dose adult formulation could be an alternative to prevent hepatitis A and hepatitis B infection in children ages 1 to 11 years.