Objective: To evaluate the immunogenicity and reactogenicity of a new triple S recombinant hepatitis B vaccine in a cohort of healthy people in whom currently licensed hepatitis B vaccines had persistently not induced an immune response.
Design: Single centre, randomised, double blind, dose-response study.
Setting: Research vaccine evaluation centre at a teaching hospital.
Subjects: 100 healthcare workers aged 18-70 years with a history of failure to seroconvert after at least four doses of a licensed hepatitis B vaccine containing the S component.
Intervention: Each subject was randomly allocated two doses of 5, 10, 20, or 40 micrograms of a new hepatitis B vaccine two months apart.
Main outcome measures: Immunogenicity of the four doses. Seroconversion and seroprotection were defined as an antibody tire > 10 IU/l and > 100 IU/l respectively against an international antibody standard.
Results: 69 subjects seroconverted after a single dose of the vaccine. After the booster vaccination one other subject seroconverted, bringing the overall seroconversion rate to 70%. Fifteen subjects given 5 micrograms of vaccine, 19 given 10 micrograms, 16 given 20 micrograms, and 20 given 40 micrograms seroconverted. Seroconversion rates in the four antigen dose groups were 60% (15/25), 76% (19/25), 64% (16/25), and 80% (20/25). After the booster dose there was no significant dose-response effect on the overall seroconversion rate, although the small sample size meant that a clinically important dose-response could not be ruled out.
Conclusion: A single dose of 20 micrograms of the vaccine was as effective as two doses of either 40 micrograms or 20 micrograms of this vaccine formulation in terms of seroconversion, seroprotection, and geometric mean titres.