Among the long list of reasons the fearful give for reasons they're not getting a flu shot - hatred of needles, skepticism about vaccines, laziness - one relates more closely to economics: cost. For while doctors urge everyone to get a flu shot, flu shots, like many other things in life, are not free. Stop by your local drugstore and you'll shell out $30 or so for the pleasure of getting poked by a needle behind a suggestion of a curtain.

So why aren't flu shots free, or nearly free? After all, they've been around for a while, and there's a lot of demand - isn't it about time flu shots cost the same as, say, generic Tylenol?

If only, said Curtis Allen, a spokesman for the Centers for Disease Control and Prevention. The real question should probably be - why does the flu shot cost so little?

It's because the process of manufacturing and distributing the flu shot is a huge headache for pharmaceutical companies. The influenza vaccine must be made anew each year, beginning in February. Researchers determine what strains to put in the vaccine after looking closely at what types of flu are most prevalent in the Southern Hemisphere throughout its winter, which is the Northern Hemisphere's summer.

Then the handful of pharmaceutical companies making the vaccine must estimate how many doses to make. Make too many, and they'll have to throw away a bunch if people don't get the flu shot; make too few, and they'll cause a panic about vaccine shortages.

Vaccines for other illnesses, such as measles, mumps and rubella, can be used until their expiration date, which is often years after they're made. Influenza vaccines are usually only used September through January and then go in the trash.

Influenza vaccines cost health care providers from $10 to $16 per dose, according to the CDC. They're by far the cheapest vaccine on the list. The tetanus vaccine costs a provider $38, human papillomavirus vaccine is $130 and Hepatitis B vaccine is $52.