Efficacy trial of heat-inactivated hepatitis B vaccine (CLB) in male homosexuals in the Netherlands.

The efficacy of a heat-inactivated hepatitis B virus (HBV) vaccine, containing 3 micrograms-HBsAg, was studied among a group of 800 susceptible homosexual men. The trial was conducted randomized, placebo-controlled and double blind. At the trial end point (21.5 months) the attack-rate for all HBV infections together was 4.8% among vaccinees and 23.8% among the placebos (p less than 0.0001). Four months after the first injection 89% of the vaccinees had formed anti-HBs and this percentage declined only slightly during the follow-up period. Maximum titers were reached 5 months after the first vaccination. None of the vaccinees who responded to the vaccine with anti-HBs greater than or equal to 1 mIU/ml developed a HBsAg positive infection. The vaccine had no serious side-effects.