Drugmakers moved one step closer to getting swine flu vaccines into your arm with approvals by the Food and Drug Administration yesterday.

Novartis (NYSE:NVS), sanofi-aventis (NYSE:SNY), and AstraZeneca (NYSE:AZN) all received approvals yesterday. Conspicuously absent from the group was GlaxoSmithKline (NYSE:GSK), although Health and Human Services Secretary Kathleen Sebelius said the FDA was working on its application.

When the vaccines hit doctors' offices in mid-October, it looks like patients will have half as many pokes as expected; the vaccine seems to work from a single injection, and a booster shot probably won't be needed. That may sound like bad news for vaccine makers, but because demand is likely to outstrip supply, it may mean the same sales, and just more people vaccinated.

If supplies are limited, AstraZeneca won't have much of an advantage with its kid-friendly inhaled flu vaccine, FluMist. Sorry, kids, you get what's available from the doctor; if it's the shot-in-the-arm kind, then so be it.

Now that most of the vaccines are approved, we can turn to the question of how many people will get vaccinated, and how awful the flu season will be. For cases that are really bad, doctors will prescribe anti-viral drugs, such as GlaxoSmithKline's Relenza or Roche's Tamiflu, from which Gilead Sciences (NASDAQ:GILD) receives royalties. BioCryst Pharmaceuticals (NASDAQ:BCRX) also has an antiviral drug, peramivir, but it's still in development. Whether countries will make emergency approvals to use that drug remains to be seen, and it may depend on whether the virus mutates and becomes resistant to Relenza and Tamiflu.

While an approval of vaccines is certainly a good thing for drug companies and the economy in general, the good news will be fleeting, we hope. The swine flu will result in a momentary boost in revenue -- although considering the size of most pharmaceutical companies, it won't be that much of a boost -- and then sales will cease and we'll go back to status quo.

I'm all for investing in the next big thing, but revenue from swine flu has the shelf life closer to that of a bacon-wrapped steak than a can of pork and beans.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Novartis is a Motley Fool Global Gains recommendation. The Fool has a disclosure policy.