Immunogenicity of a low dose recombinant DNA hepatitis B vaccine in healthy adults in Singapore

The immunogenicity and safety of a standard dose of 10 micrograms of a yeast derived recombinant DNA hepatitis B vaccine (B-Hepavac II) was compared with that of a reduced dose of 5 micrograms in 84 healthy adult volunteers with no previous exposure to hepatitis B. Each subject received either a 10 micrograms or 5 micrograms dose of vaccine intramuscularly at 0, 1 and 6 months. One month after the second injection of vaccine the seroconversion rate in the two groups were 85 and 86 percent respectively. Two months after the third injection 100 percent of participants had sero-converted; 95 percent of the 10 micrograms group and 91 percent of the 5 micrograms group had titres of anti-HBs greater than 10 IU/L. The geometric mean titres (GMT) of anti-HBs levels at 2, 6, 8, and 12 months were 34, 61, 811 and 188 IU/L in the 10 micrograms group and 26, 45, 836 and 304 IU/L in the 5 micrograms group respectively. Adverse effects were mild and transient. The vaccine was safe and immunogenic in the doses given. The reduced dose of 5 micrograms was as effective as the standard 10 micrograms dose.