Enhanced immunogenicity of recombinant hepatitis B vaccine in exposed family contacts of chronic liver disease patients

Close family contacts of hepatitis B virus (HBV)-related chronic liver dise ase patients have a high risk of exposure to HBV. Variable responses to vac cination have been reported in family contacts, especially in previously ex posed contacts (IgG antiHBc-positive). Seventy-nine healthy family contacts , who were HBsAg-negative with normal alanine amino-transferase level and n o evidence of liver disease, were vaccinated using a recombinant HBV vaccin e, irrespective of past exposure status. A significantly higher number of p reviously exposed subjects (n = 25; Group I) developed early seroprotective anti-HBs titers with 2 initial doses of vaccine compared to the unexposed contacts (Group II; n = 54) (64% vs 33%, respectively; P < 0.05). However, the responses were comparable on completion of the schedule (96% vs. 94%, r espectively). HBV DNA was detected in 11 of 25 (44%) exposed and none of th e unexposed contacts at baseline. Post-vaccination, 3 of 11 (27%) subjects became HBV DNA-negative and remained negative for the next 12 months. These results suggest that exposed family contacts achieve efficient seroprotect ion after HBV vaccination, irrespective of the IgG anti-HBc status. The res ponse to vaccination resembles an anamnestic reaction and possibly demonstr ates a therapeutic effect.