[Significance of isolated anti-HBs antibodies in subjects not vaccinated against hepatitis B viruses].

The significance of isolated anti-HBs antibodies in subjects not vaccinated against the hepatitis B virus (HBV) was investigated in 13 healthy blood donors. All were European and none had any risk factor for hepatitis B infection. Serological assays included HBV-DNA and anti-preS 2 antibody determinations which were all negative. After injection with hepatitis B vaccine (Hevac B), only one out of the 13 subjects exhibited an anamnestic response in favor of secondary immunization. Neutralization tests for serum anti-HBs antibody were positive in only 6 subjects. Our data suggest that in most cases isolated anti-HBs positivity does not correspond to true antibody; booster injection of HBV vaccine seems to be the best way of verifying that antibodies are really protective.