The authors also revisited one of the concerns raised during the 1976-77 swine flu vaccination program. The vaccine in that campaign was associated with an increased number of Guillian-Barre Syndrome cases, in which the body's immune system mistakenly attacks part of the nervous system. Guillian-Barre normally affects about one out of every 100,000 people a year. Based on this Guillian-Barre background rate, if 100 million people in the United States are inoculated in a pandemic flu vaccination campaign, the researchers said one would expect 215 new cases of the disease within six weeks of vaccine. These cases would be expected to occur whether or not the vaccine had been given.

"The reporting of even a fraction of such a large number of case as adverse events following immunization, with attendant media coverage, would likely give rise to high levels public concern, even though the occurrence of such cases was completely predictable and would have happened in the absence of a mass campaign," according to the paper.

To help address these concerns, the U.S. Centers for Disease Control and Prevention (CDC) and other health agencies have been creating systems to gather and accurately assess data on background health events when evaluating vaccine safety. The current paper presents some new data but also puts existing data into context for the public, said Dr. Black, who also serves as a pandemic flu vaccine safety consultant to the National Vaccine Program Office at the Department of Health and Human Services.

"In the heat of the moment of a pandemic vaccination campaign, the public isn't good at evaluating comparative risk or realizing that obviously some people die or develop serious illnesses every day," Dr. Black said. "By putting background rate data into proper context, we want to help people make an informed decision about pandemic flu vaccinations."

cincinnatichildrens/