Flu season is upon us, and health officials are keeping their fingers crossed that this year will play out without any of the sudden vaccination snafus that have roiled the healthcare system in years past. This year, health officials believe the United States will need about 90 million doses of flu vaccine to satisfy demand. And vaccine manufacturers have assured the Centers for Disease Control in Atlanta that 89 million to 97 million doses are on their way, says Ray Strickas, M.D., assistant director for adult immunization activities for the CDC. Strickas believes that the U.S. should be able to avoid a repeat of the last flu season, when British health officials found that the Chiron Corporation's vaccine production facility in the U.K. was contaminated and unexpectedly shut it down, erasing more than half of the United States' needed vaccine supply. Chiron recently got a clean bill of health from British regulators and the FDA and says it is preparing to ship 18 million to 26 million doses of trivalent inactivated influenza vaccine in coming months. Meanwhile, Sanofi-Pasteur projects that it will provide up to 60 million doses of TIV and Gaithersburg, Md.-based MedImmune will provide about three million doses of its nasal-spray vaccine, which so far has proved unpopular in the United States. Newly-licensed vaccine supplier GlaxoSmithKline has contracted to deliver eight million doses. But as recently as September 16 the Centers for Disease Control said that production uncertainties remained, and advised that only priority groups — especially seniors, the chronically ill, pregnant women and infants under two years of age — receive vaccines prior to October 24. "Historically, the United States has never used more than 83 million doses of flu vaccine," says Strickas. But a vaccination supply is recommended for 180 million people. "As a colleague of mine once said, we run the risk of a built-in shortage every year. It just depends on what the demand is. But we would like to enhance demand and keep the supply in line with it; that's a difficult balancing act sometimes." Complicating the balancing act is the reluctance to order more vaccine than is used in a given flu season. The FDA's license for vaccine supplies is good only until the following June, forcing suppliers to destroy any unsold stocks that remain. Analysts have also been nervously watching Chiron's comeback effort. Geoffrey Porges of Bernstein Research recently reported that Chiron has yet to have shipments approved by the FDA and has told distributors that it can expect to receive only half of the vaccine that they had expected. They were also given an option on canceling November shipments, raising fears of fresh shortages. But a number of health departments around the country have been issuing reassuring reports that sufficient supplies will be available. One exception: Detroit. A survey by the Detroit Free Press found several local doctors who have not received the vaccine they ordered. The doctors' suggestion was to go to supermarkets and drugstore chains, which ordered large numbers of doses well in advance in preparation for the fall. Preparations for the flu season start as soon as the previous season ends in May. Every year, the World Health Organization takes a close look at the strains that are in general circulation and chooses the ones that the world will be most likely to need protection against. This year, WHO picked two strains that linger from last year — A/Caledonia/20/99 and B/Shanghai/361/2002 — and one new virus, A/California/7/2004. Vaccines are formulated with those strains in mind. But health officials also note that even if a new strain develops, the existing vaccines can often help people reduce complications and soften its impact. Young people can expect that a vaccination will be 50 percent to 90 percent effective, but elders can only expect vaccinations to be 30 percent to 40 percent effective. Even in a good year, 65 million can be expected to contract the flu, 200,000 will be hospitalized and 36,000 will die. A potentially lethal wild card in the vaccine business could come from a new form of avian flu that could be spread from human to human. Federal officials, led by President Bush, sounded the alarm after a late-September meeting that reviewed the chances of a pandemic breaking out if the bird flu virus H5N1 were to mutate and spread among a human population. That scenario has a number of state health officials scrambling to dust off emergency plans. Tennessee is joining North Carolina, Kentucky, Virginia and West Virginia in a five-state drill in October to evaluate their readiness. And the United States has begun contracting for supplies of Tamiflu, a flu vaccine that has shown signs of treating the symptoms of avian flu. But researchers also note that until there is an actual mutation, researchers won't be able to start designing a vaccine that will specifically target the disease.