The vaccine Twinrix (produced by G1axoSmithKline, SmithKline Beecham Biologicals, Rixensart, Belgium) has been available worldwide for more than 4 years. In the Czech Republic it is registered since 1998. This year the results were published of an extensive investigation pertaining to the clinical evaluation of subjects who were immunized by the combined vaccine against both types of hepatitis in 1993 and 1994 and where the results of the immune response were available at different time intervals, i.e. from month 18, 24, 36, 48, 60 and 72 depending on the age cohort involved. Anti-HAV seroconversion was uniform and reached in all investigated age cohorts and at all time intervale values of 100%. Anti-HBs seroprotection is not so uniform bul despite this it gives excellent results as it reached values of 89 to 95%. In the course of time the GMT (geometrie mean titre) declined being most marked during the first 12 months after completed vaccination. On the basis of the presented data we may stale responsibly lhal after vaccination of children and adults with Twinrix vaccine using the basic vaccination schedule it will not be necessary to boost after £ve years. Most probably the immunity after completed vaccination (Day-0, Month-1, Month-6) will have a long-term character (more than 15 years) and may be, it will be lifelong. Such a conclusion may be foreseen in a fully competent subject who responded verv well to the basic vaccination. Therefore it is recommended nowadays to assess antibody titres on month after termination of the vaccination. If the anti-HBs values are z 10 mIU/ml and anti-HAV Z 20 mIU/ml then we may foresee long-term protection against VHA and VHB.

        Key words: Twinrix, long-term immunity, revaccination, víral hepatitis A, víral hepatitis B