Long term observation of the effect of intradermal hepatitis B vaccination on mentally retarded patients.

Sixty-two patients of two institutions for mentally retarded patients were immunized intradermally with 4 micrograms doses of plasma-derived hepatitis B vaccine made in Japan, initially at month 0.1 and 6. The three vaccinations induced antibodies in 93.5% (90.9% in those with Down's syndrome (DS), 94.1% in other forms of mental retardation (OMR) of the vaccinees within 9 months after the first injection, and the percentage of geometric mean titers of antibody above 10 mIU/ml was 89.3% (81.8% DS, 84.3% OMR) within 9 months. Within 2 years, the seroconversion rate showed a significantly higher decrease in subjects with DS (54.5%) than in OMR (86.3%), and the percentage of vaccines with above 10 mIU/ml also showed a significantly higher decrease in subjects with DS (36.4%) than in those with OMR (74.5%) (p less than 0.05). In the OMR patients, the antibody response persisted for 2 years, decreased remarkably in the DS patients.