With the flu season upon us, the U.S. Food and Drug Administration worked hard to round up as many vaccine manufacturers as possible this year to avoid a repeat of the shortages experienced last year.

In particular, it gave pharmaceutical giant GlaxoSmithKline (NYSE:GSK) the green light to begin production of its Fluarix vaccine that is currently available in 79 countries around the world. Glaxo expects to produce as many as 8 million doses of its adults-only variety, or double the amount it provided last year, to shore up the dearth of vaccines caused as a result of Chiron's (NASDAQ:CHIR) contamination problems.

The nation's Centers for Disease Control optimistically reports that the U.S. may have as many as 97 million doses available this flu season -- almost as many as should have been available last year -- yet it is giving us a best-case scenario for which there are definitely no assurances.

In addition to Glaxo, Sanofi-Aventis (NYSE:SFY) is expected to once again provide the yeoman's share with 60 million doses, while beleaguered Chiron is hoping to provide anywhere from 18 million doses to 26 million -- anywhere from one-half to two-thirds less than the number it was supposed to cough up in the 2004 season. This year again, it's Chiron causing the uncertainty; its manufacturing capabilities, while expected to be restored, are still a big question mark.

Additional vaccine will be manufactured by MedImmune (NASDAQ:MEDI), which forecast 3 million doses of its FluMist nasal spray vaccine.

That makes four vaccine manufacturers this year. While that's double the number that were producing vaccine in this country at the start of the flu season last year, it's still a far cry from the 10 manufacturers in the early 1990s that were producing protection from the potentially deadly flu virus -- the CDC estimates 36,000 people a year die from it -- and only a fraction of the 26 manufacturers in existence in the 1960s. A combination of government regulation and pricing pressures led to the demise of the once-thriving vaccine industry.

While the current egg-based vaccine can't be stockpiled year to year, promising developments from Crucell (NASDAQ:CRXL) and Baxter International (NYSE:BAX) may make cell-based varieties, which can be stored until needed, available sooner rather than later. ID Biomedical (NASDAQ:IDBE) has had its Fluviral vaccine, currently in use in Canada, fast-tracked for approval for the 2006 flu season.

But the real threat against which we urgently need to protect ourselves is a flu pandemic for a form of the flu for which there are no vaccines available, such as avian flu. A worldwide outbreak of these viruses could cause widespread death of Biblical proportions. The National Institutes of Health awarded contracts to Chiron and Aventis in April to produce and test an investigational bird flu vaccine. With more than 110 cases of the virus surfacing in Asia since the start of 2004, their need grows more acute daily.

That said, the country still needs to come to grips with the more pedestrian varieties of influenza that occur annually. To that end, the CDC is proposing rationing the vaccines again -- at least until the end of October. As the flu season progresses, all eyes (even those that are red and watery) will be on Chiron to see how well it stands up to the test.

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Fool contributor Rich Duprey does not own any of the stocks mentioned in this article. The Motley Fool has an ironclad disclosure policy.