Modelling long-term persistence of hepatitis B antibodies after vaccination

Antibody response to hepatitis B vaccination was measured in 97 institution alized, mentally handicapped patients after a 0-, 1-, 6-month vaccination s chedule. Two groups were formed at month 7 according to the antibody respon se, which determined whether they needed an additional vaccine dose at mont h 12, to achieve an antibody titre of 100 IU/liter. All residents were foll owed up yearly for the first 5 years, after which, they received another bo oster dose. Another blood sample was taken 11 years after the start of the program. A linear mixed-regression model was used to analyze the data. Rand om and fixed effects were included to determine the generally known risk fa ctors and the still unknown individual characteristics that influence the t itre of hepatitis B surface antibodies (anti-HBs), The mean anti-HBs titre was a function of time, type of mental retardation (Down's syndrome or othe r types of mental retardation), the use of antiepileptic drugs, and the add itional booster at month 12. The immediate and vigorous response of the imm une system to booster vaccination shows that the immunologic memory is good after primary vaccination. For the maintenance of protection, the recommen dation for mentally retarded patients in institutions is vaccination of all seronegative residents as well as new entrants, after which, no additional boosters will be necessary. (C) 1999 Wiley-Liss, Inc.