Flu vaccine forecast raises several possible outcomes

Washington -- Three vaccine scenarios are being eyed by the Centers for Disease Control and Prevention for the upcoming flu season: rain, shine or hurricane.

A "rainy" scenario, the one the agency considers realistic, would mimic last season's scattered storms of accessibility. The supply would be about 60 million doses of injectable flu vaccine and 3 million doses of nasal vaccine, said Lance E. Rodewald, MD, director of the CDC's Immunization Services Division, speaking during last month's 39th National Immunization Conference in Washington, D.C. The conference, sponsored by the CDC, brought officials together to assess the most recent flu season and look to the upcoming one.

Public health officials also considered the possibility of a sunnier forecast for the 2005-2006 flu season -- one that includes plenty of vaccine for all.

But at the same time, they also must not overlook the flu vaccine equivalent of a devastating hurricane. If this forecast pans out, physicians would have less vaccine to offer than last time around, said Dr. Rodewald.

About 43% of adults considered to be in high-priority categories for vaccination received shots last season, compared with nearly 48% the previous season, said Jeanne Santoli, MD, deputy director for CDC's Immunization Sciences Division. That fairly high vaccination rate, despite the loss of nearly half of the expected supply of vaccine, occurred because more than 16 million healthy adults deferred immunization, she said.

Last season's shortage occurred when British health officials shut down Chiron Corp.'s flu manufacturing plant, leaving sanofi pasteur, formerly Aventis Pasteur, the only supplier of injectable vaccine licensed for use in this country.

However, Chiron is expected to be producing vaccine again after receiving authorities' go-ahead, and the Food and Drug Administration is working to license another manufacturer. If that license is approved, a best-case scenario could evolve, said Dr. Rodewald, and more vaccine than 63 million doses could result.

"Unfortunately we have to plan for a worst-case scenario," he added. "What if there's a production failure at sanofi pasteur and there are no other manufacturers?" In that case, Dr. Rodewald is predicting a hurricane.

Only in the event of a worst-case scenario would the CDC consider purchasing vaccine from an unlicensed supplier as was done last season, said Dr. Rodewald. None of that vaccine, which was categorized as an investigational new drug and would have required patients to sign consent forms, was used, he said.