Immunogenicity of a DNA-recombinant hepatitis B vaccine (Engerix B) given at 3, 5 and 11 months of age with a new schedule suitable for mass vaccination programmes.

Following the demonstration of a fully satisfactory immunogenic activity of a hepatitis B vaccination protocol consisting of three doses given at the 3rd and 5th months of age with a booster at 11, it was possible to administer this vaccine at the same times as the vaccinations for diphtheria, tetanus and polio which are mandatory in Italy at those ages. A field trial of this protocol in a hyperendemic area near Naples (prevalence of HBsAg about 14%) started on January 1987. The French vaccine, Hevac B, Pasteur, was used. At this time compliance is 99%, and fully satisfactory results both in terms of seroconversion rate (96.3%) and of mean anti-HBs titre (4,352 mIU/ml) two months after the booster dose have been obtained. In this paper we demonstrate that even for a new hepatitis B vaccine prepared by a DNA-recombinant technique (Engerix B, SK & F) recently introduced in Italy, the same schedule can be used. In fact two doses of this vaccine, the first given at three months of age and the second two months later, resulted in a 100% seroconversion rate and a mean anti-HBs titre of 560 mIU/ml. Two months after the booster given at 11 months of age the mean anti-HBs titre was 12,100.