Generally, flu viruses are easily transmitted from person to person, but so far, the H5N1 avian influenza viruses have not demonstrated this characteristic. In the worst-case scenario, if an avian flu virus became easily transmissible from person to person, it could trigger an influenza pandemic because humans have no pre-existing immunity to these viruses.
The trial, conducted between March and July 2005, was carried out at three NIAID-supported Vaccine and Treatment Evaluation Units located at the University of Rochester Medical Center in Rochester, NY; the University of Maryland School of Medicine Center for Vaccine Development in Baltimore; and the Los Angeles Biomedical Research Institute at Harbor-University of California, Los Angeles, Medical Center. John Treanor, M.D., of the University of Rochester, led the group.
The study was conducted in two stages. In the first stage, the research team enrolled 118 healthy adults ages 18 to 64 years old. Each participant was assigned at random to one of five groups. Volunteers in each group received an initial dose of vaccine (7.5 micrograms [mcg], 15 mcg, 45 mcg or 90 mcg) or saline placebo into the upper arm muscle; about one month later, they received a booster shot of the same vaccine dosage or the placebo. The research team collected blood samples before each vaccination and one month after the second vaccination.
Before the study could be expanded, an independent Data and Safety Monitoring Board assessed the vaccine's safety by reviewing data collected through day 7 after the second vaccination; no safety concerns were found. The investigators then began stage two of the study, eventually enrolling an additional 333 healthy adult volunteers into the trial according to the same protocol design as in stage one.
The NEJM article describes an analysis of data on the safety and immune responses to the vaccine. In general, the higher the dosage of vaccine, the
Source:NIH/National Institute of Allergy and Infectious Diseases