IMMUNOGENICITY OF STANDARD AND LOW-DOSE VACCINATION USING YEAST-DERIVED RECOMBINANT HEPATITIS-B SURFACE-ANTIGEN IN ELDERLY VOLUNTEERS

There is no conclusive evidence that age influences the response to va ccination against hepatitis B virus. We therefore studied the immunoge nicity of yeast-derived rHBsAg vaccine in elderly volunteers. The stud y was conducted in the outpatient clinics of an academic and a regiona l hospital, in a rural family practice and in an urban community centr e. We recruited 112 healthy volunteers aged 59 years and over, to whom 10 or 20 mu g yeast-derived HBsAg was given at 0, 1 and 6 months. Ant i-HBs titres were measured by radioimmunoassay at 2, 6 and 7 months. R esponders and non-responders were compared using univariate non-parame tric tests and multivariate logistic regression analysis. Of the 116 s ubjects who volunteered to take part in the study, 106 vaccinees compl eted it. The percentage of subjects with an anti-HBs titre greater tha n or equal to 10 IUl(-1) at 7 months was 60% (95% confidence interval: 51-70%; geometric mean titre: 253 IUl(-1)). Of the factors studied, i .e. setting, age, sex, alcohol consumption, current medication and vac cine dose, the use of medication at the time of the first vaccination was the only independent factor related to the response to vaccination , with a response rate of 78% (95% confidence interval. 66-89%) in tho se without medication. In elderly subjects, the proportion with protec tive concentrations of anti-HBs after vaccination with 10 or 20 mu g y east-derived recombinant HBsAg in a standard scheme is lower than in h ealthy adolescents. Within the older age group studied here, the use o f medication, probably reflecting general health, is the only signific ant factor influencing the response to vaccination.