The never-ending story: Flu vaccine season goes year-round

After several rocky seasons, this year's stock of influenza vaccine has been arriving on time, or even before physicians expected it. "This year was good news," said Stuart Sanders, MD, an internist and sports medicine physician in Demorest, Ga. "There was no problem getting our full shipment of flu vaccine."

His 1,350 doses arrived by the end of August, a far cry from previous years when supplies arrived late or not at all. Some 143 million to 146 million doses are expected before the season is done, and all five manufacturers have been shipping since early August.

"This is really quite a technical achievement that [manufacturers] are rising to this challenge and are on a faster timeline than in previous years," said Bruce Innis, MD, vice president for clinical research and development at GlaxoSmithKline.

Medical societies and public health agencies have long been working to stabilize the supply chain. The American Medical Association and the Centers for Disease Control and Prevention, for example, have organized the National Influenza Vaccine Summit, which meets annually and holds conference calls regularly during flu season. The AMA also advocates that physicians serving high-risk populations receive influenza vaccine in a timely and equitable manner.

Improvements in the supply chain are due to these efforts as well as a combination of business changes and scientific advancements that have made the vaccine's journey more efficient.

On the business side, more companies are in the game, making a repeat of the 2004-05 season less likely. At that time, one company, Chiron Corp., had sterility problems in its manufacturing facility, and 46 million to 48 million doses -- nearly half of the total expected supply -- were lost. This left Sanofi Pasteur, then Aventis Pasteur, which initially planned to deliver 52 million doses, as the sole manufacturer of injectable vaccine. Production ramped up, and the company delivered about 58 million doses. MedImmune Inc. created 3 million doses of the intranasal version.

This season, five companies are involved. Sanofi Pasteur expects to ship 50 million doses, and CSL Limited is supplying 6 million. Novartis, which purchased Chiron in 2006, will manufacture 40 million shots, and GSK plans to provide 35 million to 38 million. MedImmune will make 12 million doses of the intranasal version.

Science also is speeding the process. Manufacturers increasingly are using reverse genetics to hasten production of seed viruses. They also are working to develop cell culture production, which is expected to increase capacity and make supplies more predictable. Cell culture would be particularly useful to deal with a pandemic in which the virus also affects birds, since chickens produce the eggs required to make the vaccine.

"The key thing is that it takes chickens out of the mix," said Matthew Stober, global head of technical operations for Novartis.

In the research world, investigators also are looking at vaccine formulations that would not need to be changed annually.

Data on a phase I study of a vaccine for all influenza A viruses will be presented at an October joint meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America, to be held in Washington, D.C. The findings suggest this vaccine creates a good immune response and is well tolerated.

"[This] has the potential to be a safe, highly effective and much-needed option to prevent seasonal and pandemic influenza," said Christine Turley, MD, the study's primary investigator and director of clinical trials and research at the Sealy Center for Vaccine Development at the University of Texas Medical Branch in Galveston.

This formula does not rely on cell- or egg-based production processes. Instead, vaccine antigens are produced more quickly by combining toll-like receptor-mediated immune enhancers and recombinant bacteria.