MedImmune (NASDAQ:MEDI) has looked a bit under the weather this weekend, despite the hoopla over its new FluMist influenza vaccine. While MedImmune and co-promoter Wyeth (NYSE:WYE) issued a press release Thursday reminding people that its painless vaccine option was included in influenza vaccine recommendations, the stock took a 6% hit Friday (an admittedly tough day for biotech).

FluMist is without doubt an exciting innovation. So much for the dreaded needle -- FluMist is inhaled through the nose. And the flu season, which starts in November, is fast approaching.

In addition, the vaccine will be offered at your friendly neighborhood Wal-Mart (NYSE:WMT), scoring points for convenience as well.

While many analysts see dollar signs for FluMist, there are reasons to ponder the real-world revenue potential. For one, FluMist, which is composed of a diluted but live influenza virus, is only approved for healthy people aged 5 to 49. While the flu impacts us all, this is not the age group that is traditionally at the highest risk. To further complicate matters, according to the Centers for Disease Control, a scant 13% of healthy Americans in that age group bother to get flu vaccines at all.

Second, there's FluMist's price tag. It's expected to retail at an average of $46, with the high end possibly as high as $75 -- talk about ouch. (In comparison, the needle vaccine -- offered by Aventis SA (NYSE:AVE) and Chiron Corp. (NASDAQ:CHIR) -- generally costs somewhere in the neighborhood of $10 to $20.)

If insurance companies are willing to pony up (and so far, some are at least providing partial reimbursement), that would certainly help FluMist gain some traction. However, we all know that insurance companies often don't pay top dollar for a product when a cheaper alternative is as effective.

By the same token, will a bargain-shopping Wal-Mart family part with several hundred dollars for a snort of nose spray all around? Seems like a minute of discomfort for the low-priced version could be worth it to all but the most financially comfortable.

One of Friday's most active stocks, MedImmune closed at $32, down 24% from its 52-week high. Despite high hopes for the draw of needle phobia, it seems investors may be getting a little injection of doubt.

Alyce Lomax welcomes your feedback at [email protected].