Tis the season to be jolly, and also for the flu to strike millions of people. The virus may not be nearly as dangerous and lethal as it used to be -- the disease kills 300,000 to 500,000 people worldwide every year, but the 1918 flu pandemic killed 50 million to 100 million people. However, with fears over the avian flu, and the stockpiling of millions of doses of drugs like Roche's Tamiflu to treat the various forms of the disease, there are billions of dollars to be made by the pharmaceutical companies that are treating and preventing the flu.

Not only does treating the flu prevent people from having to deal with the runny noses and other symptoms of the infectious disease, but flu prevention can also save employers from the costs of lost productivity due to time off from work. According to the aptly named consulting firm Challenger, Gray, and Christmas, employees will miss 70 million days of work because of the flu, adding up to $10 billion in lost wages for companies as a result of paid sick leave.

The amount of these lost wages has led to a rapid growth in the market for influenza vaccines. In 2005, Sanofi-Aventis (NYSE:SNY) had sales of $819 million for its flu vaccines, up 29% over 2004; Chiron (now part of Novartis (NYSE:NVS)) sold $97 million worth of its flu vaccines in 2005 despite experiencing severe manufacturing issues for much of the year. The other player in this field is MedImmune (NASDAQ:MEDI); its FluMist product achieved only $21 million in 2005 sales, but a next-generation product named CAIV-T hopefully will be coming to the market sometime next year.

Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy .