Hepatitis B vaccination in mentally retarded: effectiveness after 11 years

The long-term effectiveness of hepatitis B vaccination was determined in a high-risk group of 105 institutionalized mentally retarded. All individuals were vaccinated in 1986, with three (0, 1, 6 months), four (0, 1, 6 and 12 months) or more doses according to their immune response at month 7, resulting in group 1 (G1), group 2 (G2) and group 3 (G3). They were annually followed up for five years, after which they received a booster dose. Eleven years after the initial vaccination, they were again tested for the presence of hepatitis B virus (HBV) serologic markers. The decline in anti-HBs logtitre over the first five years was 51% for G1 and 45% for G2. From the booster on month 60 to year 11, the overall decline was 31%. Eleven years after the start of vaccination and six years after the booster, 92% of the individuals had protective antibody levels higher than 10 IU/L. G1 had a geometric mean titre of 2015 IU/L, for G2 this was 245 IU/L. The difference in response to vaccination between the groups did not affect their protection. Only two vaccinees seroconverted to anti-HBc positivity without becoming carrier or ill. Long-term protection against HBV by vaccination appears to be excellent.