Radioimmunoassay for antibody to hepatitis B surface antigen shows transmission of hepatitis B virus among household contacts.

The epidemiology of infections with hepatitis B virus was studied by measurement of serum antibodies to hepatitis B surface antigen (HBS Ag) with the radioimmuno-precipitation test. Prospective studies of household contacts of HBS Ag-positive patients with acute hepatitis demonstrated that four of 41 children and one of 60 adults experienced anicteric seroconversions. Two of the 60 adults also had mild icteric hepatitis and became chronically antigenemic. Neither HBS Ag nor antibody to HBS Ag was detected in follow-up blood samples from 85 seronegative contacts of HBS Ag-negative patients with hepatitis, although seven icteric secondary cases were identified. Household contacts of HBS Ag carriers frequently had serologic evidence of exposure to hepatitis B virus (44% of adults), but the remainder had neither detectable antigen nor antibody.