Poor seroconversion rate after hepatitis B vaccination in high-risk institutionalized mentally retarded patients

We studied the rate of seroconversion to positivity for antibody to hepatitis B surface antigen (anti-HBs) after immunization with hepatitis B vaccine in a group of mentally retarded institutionalized patients. Eight hundred sixty-eight individuals were screened for seromarkers of hepatitis B infection (hepatitis B surface antigen and anti-HBs), and 287 seronegative patients were vaccinated with the recommended schedule of hepatitis B virus vaccine (20 micrograms IM at 0, 1, and 6 months). Overall, 59% of patients responded to vaccination with detectable anti-HBs. We found a high correlation of lack of response with both intragluteal injection and increasing age (p less than 0.0008), although the design of the study did not allow these factors to be analyzed separately. We conclude that buttock injection and advancing age may be risk factors for poor immunogenicity of the hepatitis B vaccine in mentally retarded populations.