A controlled, randomized, double-blind trial in 1,083 homosexual men from New York confirmed that a highly purified, formalin-inactivated vaccine against hepatitis B prepared from HBsAg positive plasma, is safe immunogenic, and highly efficacious. Over 95% of vaccinated subjects developed antibody against the surface antigen. Vaccine-induced antibody persisted for the entire 24-month follow-up period. The attack rate of all hepatitis B virus infections (excluding conversions of anti-HBc alone) was 3.2% in vaccine recipients compared with 25.6% in placebo recipients (p less than 0.0001). In those who received all three doses of vaccine, of 40 micrograms each, the protective efficacy rate was close to 100%. The vaccine protects against acute hepatitis B, asymptomatic infection, and chronic antigenemia. There is reason to assume that the vaccine is also partially effective when given postexposure.

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We evaluated the efficacy of hepatitis B vaccine (Heptavax-B) containing only the ad subtype in a randomized, placebo-controlled, double-blind trial among 865 staff members of 43 hemodialysis units in the United States. Surface antibody developed in 92.6 per cent of the subjects after two doses of vaccine and in 96 per cent after the six-month booster. The incidence of infections with hepatitis B virus (with or without hepatitis) was 9.9 per cent in placebo recipients and 2.2 per cent in vaccine recipients (P less than 0.01). The two cases of hepatitis B among vaccine recipients did not occur in subjects in whom antibody had developed. In 81 per cent of the hepatitis events, the virus was of the ay subtype. The indicence of ay virus was 8.2 per cent among placebo recipients and 1.2 per cent among vaccine recipients (P less than 0.005). We conclude that these data confirm the efficacy of the vaccine and demonstrate subtype cross-protection.