Hospitals in seven European nations have started an international Phase III clinical trial of H5N1 influenza pandemic vaccine. The trial is designed to assess the response of antibodies and the possible side effects of H5N1 influenza pandemic vaccine in adults.
The vaccine under study is fractionated, meaning it only contains parts of the viral proteins that activate the human immune system and therefore cannot cause influenza. But it does contain an adjuvant that enhances immunogenic effects, allowing a reduced concentration of vaccine in each dose.
Officials say 5,052 volunteers will participate in the study. They will be randomly separated into two groups -- 75 percent who will receive two doses of influenza vaccine, and 25 percent who will receive a dose of conventional influenza vaccine and a dose of placebo.