[Use of hepatitis B virus vaccine in volunteer donors already immunized against this virus]

Forty nine blood donors immune to HBV have been volunteers to receive a single dose of hepatitis B vaccine (Hevac B from Pasteur Institute Production). The initial mean level of anti-HBs was 20 IU/ml (from 5 to 75 IU/ml). The maximum level was observed at the consecutive plasma donation usually 1 month and a half after the vaccine injection. The mean maximum level was 188 IU/ml (from 7 to 800 IU/ml). i.e. an increase of 9 times the initial level. Six donors have developed a very weak immune response (inferior to twice the initial level). In the 43 others, anti-HBs levels remained higher than initial level 6 months after the vaccine injection. One year later (study conducted in 25 subjects), 56% had anti-HBs levels superior to 3.6 to 16 times the original level. Such booster responses are of considerable practical importance for increasing anti-HBs titers in human donors for producing HBIG.