Intradermal hepatitis B vaccination for mentally retarded patients.

We investigated immune responses in 63 mentally retarded patients each given a low-dose (4 micrograms) intradermally of plasma-derived hepatitis B vaccine made in Japan and which was repeated after 1 and 6 months. Two doses of the vaccine induced antibodies in 85.5% these patients. A further dose 6 months later induced antibodies in 93.5% of the recipients and markedly increased the proportion of recipients with acceptable or high concentrations of antibody. The numbers of acceptable and high responders decreased slightly during a period of 12 months. The rate of acquiring antibody was significantly higher in the males. No significant differences in antibody response with regard to age and type of disease were observed. One patient with Down's syndrome, who acquired a low concentration of antibody after vaccination, was infected with hepatitis B virus. Supplementary vaccination may be necessary for poor responders in order to obtain protection. Side-effects resulting from the vaccination were not severe in any patients. These results suggest that low-dose, intradermal hepatitis B vaccination is safe and effective.