Long-term persistence of antibodies induced by vaccination and safety follow-up, with the first combined vaccine against hepatitis A and B in children and adults

It is important to monitor the long-term persistence of antibodies induced by vaccination. Four cohorts were followed for their long-term immunity aft er vaccination with a combined hepatitis A and B vaccine (Twinrix; SmithKli ne Beecham Biologicals, Rixsenart, Belgium). Two cohorts of adults (ages 17 -60 years), one of 1-6-year-olds, and one of 6-15-year-olds were vaccinated following a 0, 1, and 6-month schedule. Followup data until month 72 (adul ts) and month 60 (children) are available. At month 72, antibody to hepatit is A virus (anti-HAV) seropositivity (S+) was 100% for both adult cohorts ( n=40 and n=47) and 95% and 89% of the vaccinees were seroprotected against hepatitis B virus (HBV), respectively. The geometric mean titres (GMTs; mIU /ml) for anti-HAV were 977 and 542 and the GMTs for the antibody to hepatit is B surface antigen (anti-HBs) were 322 and 90. For 1-6-year-olds at month 60 (n=39), anti-HAV S+ was 100% with a GMT of 479 and 97% were protected a gainst HBV with a GMT of 195. At month 60 for the 6-15-year-olds (n=42), an ti-HAV S+ was 100% with a GMT of 990 and 95% were protected against HBV wit h a GMT of 263. There have been no safety issues during the follow-up. In t he past 5 years, a postmarketing surveillance system was available. Using t his system, all spontaneous adverse events are collected and archived. Alth ough infrequent, the most commonly reported adverse events after more than 13 million doses were allergic-type reactions followed by fever and injecti on site reactions. The combined hepatitis A and B vaccine is safe and is we ll tolerated. Immunity provided by the vaccine remains high in adults and c hildren with comparable results to those obtained with monovalent vaccines. (C) 2001 Wiley-Liss, Inc.