Large-scale efficacy trials of hepatitis B vaccines in the USA: baseline data and protocols.

The protocols of three placebo-controlled, randomized, double-blind clinical trials to assess the efficacy of an inactivated hepatitis B vaccine in dialysis patients and staff, and in male homosexuals are described. Based on the projected attack rates of HBV in the controls, the vaccine efficacy and rates of loss to follow-up, over three thousand participants followed for at least twelve months are required to prove the efficacy of the vaccine. The results of longterm baseline studies in these populations are also reviewed.