The H5N1 subtype of influenza A virus has spread through bird populations in other countries. Small numbers of humans who became sick with the strain have received severe infections, and some deaths have resulted due to direct contact with infected birds.

The subtype has not yet been detected in any birds, animals or humans in the United States. However, the virus has spread to a number of new countries over the past few months and could eventually mutate into a form that spreads easily among people, said Patricia Winkour, M.D., associate professor of internal medicine in UI Hospitals and Clinics and the UI Roy J. and Lucille A. Carver College of Medicine, who is leading the UI portion of the study.

"The emergence of this influenza virus makes it urgent for us to prepare for a potential influenza pandemic," said Winokur, who also is a physician and researcher with the Veterans Affairs Iowa City Health Care System.

An inactivated vaccine was developed for the H5N1 strain. Although previous research showed that the vaccine is well tolerated, the immune response was not as strong as expected, even among people given the highest dose of the vaccine. Two doses currently are needed to prompt even a moderate immune response, making it difficult to stockpile vaccine for millions of people.

As a result, the researchers want to see if a vaccine additive, called an adjuvant, can help produce a strong response while using a smaller amount of vaccine per person.

"The new study will determine whether the adjuvant aluminum hydroxide can improve the antibody response to the vaccine," Winokur said.

"Adjuvants already are used in many vaccines and can produce a stronger immune response than vaccine proteins used alone."

The research team will compare the immune responses and reactions of participants given one of eight different doses of the bird flu vaccine.

Four different dilutions of influenza vaccine will include the adjuvant and will be compared to comparable vaccination doses that do not contain the adjuvant.

A total of 600 participants will be enrolled in the study, including 100 at the UI. The study is led by the University of Maryland. The other study sites are Cincinnati Children's Hospital Medical Center, Baylor College of Medicine in Houston, University of Rochester and University of Washington.

Men and women age 65 and older are invited to participate in the study. Participants must be in overall good health. Individuals who are allergic to eggs or have had severe reactions to a flu vaccine are not eligible to participate.

For more information on the study, call 319-384-7245 or 319-384-9569 between 8 a.m. and 5 p.m. Monday through Friday.

For more information:

National Institutes of Health

Patricia Winkour, M.D.

Iowa City VA Health Care System