Antibody to hepatitis B antigen (Australia antigen) among residents of a Finnish institution for the mentally retarded.

Sera from 521 residents of an institution for the mentally retarded near Helsinki, Finland were examined by a hemagglutination assay to determine the distribution and titers of antibodies to hepatitis B surface antigen (anti-HBs). 36.1% were found to contain anti-HBs. Factors were identified which are related to the presence or absence of anti-HBs in this population. A documented past history of hepatitis, living in "asocial" wards in which at least one HBsAg carrier was present, long institutionalization (is greater than 10 yrs.), admission to the institution between ages 5 and 19, a present age between 20 and 39, and being male were associated with the presence of anti-HBs. 43.5% of the males but only 22.2% of the females had antibody. Down's syndrome patients had lower titers but not lower frequencies of anti-HBs than the non Down's patients.