Polypeptide micelles with relative molecular weights of 25,000 (p25) and 30,000 (gp30) daltons were prepared from native 22-nm hepatitis B surface antigen (HBsAg) particles. This p25/gp30 complex was alum-adsorbed, and three dosage levels (20 micrograms, 4 micrograms, and 0.8 micrograms) were administered at 0, 1, and 6 months to 51 human volunteers. Local and systemic reactions were clinically insignificant, and all vaccinees seroconverted, regardless of dose. As anticipated, antibody responses diminished as the dosage was reduced. Seroconversion rates and geometric mean antibody levels for the 20 micrograms dosage group were significantly better than those observed with a commercial vaccine and were comparable to those achieved after immunization with 40 micrograms of the intact 22-nm particles used to prepare the polypeptides. By 2 weeks, an anti-HBs response was elicited in 80% of the group receiving 20 micrograms of the polypeptide vaccine. This rapid response to immunization may be particularly beneficial for postexposure prophylaxis where the early development of immunity is advantageous.

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Institutionalized patients with Down's syndrome (DS) are uniquely predisposed to develop chronic hepatitis B infection following exposure. Therefore vaccination is particularly warranted, but there have been concerns that these individuals may react suboptimally. We examined the immune responses of 62 institutionalized patients with DS to 20 and 40 micrograms of hepatitis B vaccine inactivated (Heptavax-B) over one year. The subjects were matched by weight, age, and sex. Seroconversion rates and levels of antibodies to hepatitis B surface antigen (anti-HBs) were comparable to those found in a normal population and were higher than those found in immunocompromised patients undergoing hemodialysis. The anti-HBs levels were consistently higher in the 40-micrograms vaccine group. In patients with DS who were over 30 years old, age was a significant factor in predicting anti-HBs responses. Conversely, in younger subjects, weight was negatively correlated with anti-HBs levels. These data clearly indicate that patients with DS respond normally to hepatitis B surface antigen vaccination and need not be considered a special group when guidelines for vaccination are recommended.

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