Protective efficacy of a recombinant DNA vaccine against hepatitis B in male homosexuals: results at 36 months.

An open study with a recombinant DNA yeast-derived hepatitis B vaccine (YDV) was carried out in homosexual men to assess the protective efficacy of this vaccine. A total of 278 seronegative volunteers were enrolled to receive three intramuscular doses of either 20 or 40 micrograms at months 0, 1 and 6. Serum specimens were taken at various times up to 36 months; relevant information regarding the occurrence of other sexually transmitted diseases (STDs) and sexual behaviour was also collected annually. One month after the third injection, the seroconversion rate in both groups was 99%. The geometric mean anti-HBs titre at this time was higher for subjects receiving 40 micrograms doses although a similar percentage of the vaccinees had titres greater than 10 mIU ml-1 in both groups. Compared with a historical control group in which the annual incidence of hepatitis B infection was 12%, only two vaccinees developed markers of infection during the immunization period and none thereafter. While an important increase in the use of condoms was noted during the 1984-87 study period and the incidence of some STDs declined, these changes could not solely account for the decrease in hepatitis B infection in the study population.