The Duke study is part of a multicenter trial that will test a modified form of an investigational bird flu vaccine to determine whether the vaccine still triggers a strong immune response at lower doses.
The seven-month trial is sponsored by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. Also participating in the study are the University of Maryland, the University of Rochester and Baylor College of Medicine.
"We hope that by adding a compound called an adjuvant to the vaccine, we can create a stronger immune response to smaller doses of the vaccine," said Emmanuel Walter, M.D., associate director of the Duke Clinical Research Institute's Primary Care Research Consortium and leader of the Duke study. "If the smaller dose stimulates immunity against the virus, then more people could be immunized with existing supplies if a pandemic occurs," he said.
The study will use an inactivated flu virus vaccine based on a strain taken from a Vietnamese patient in 2004. "There is no live flu virus in the vaccine, and there is no risk of volunteers contracting bird flu or spreading it to others," Walter said.
The vaccine is designed to protect against the H5N1 strain of bird flu that has infected poultry in Asia, Europe and Africa and killed 101 humans. Initial trials in healthy adults showed the vaccine was safe and produced an immune response but required high doses and at least two injections to initiate a strong response, Walter said.
Trial participants will receive varying strengths of the H5N1 vaccine, either with or without an aluminum hydroxide adjuvant. An adjuvant works by increasing the body's immune response to a vaccine, Walter said. Aluminum hydroxide is commonly used in pediatric and adult vaccines, including those for wh ooping cough, hepatitis A and hepatitis B.
As with current flu vaccines given yearly in the U.S., the H5N1 vaccine causes the body's immune system to make antibodies to fight infection. In previous studies with this vaccine, two doses were necessary to stimulate antibodies. The doses needed to trigger antibodies were also much higher than necessary for other types of flu, Walter said.