In the USA, the CDC (Center for Disease Control) is recommending that everyone over the age of 6 months get vaccinated, and then they go on to list those who are at specially high risk, which is very similar to what CS posted in terms of higher risk factors.

http://www.cdc.gov/flu/about/season/flu-season-2012-2013.htm#get-vaccinated

I'm guessing the difference in recommendations reflects the differences in our health care systems and how they are funded, i.e., in the UK, with a primarily tax-funded health care system, they give more consideration to the costs vs. the risks when formulating recommendations. A more rationed system. In the USA, where a significant amount of health care is still paid for through private sector insurance, the cost/benefit analysis by a government agency is weighted differently. With the upcoming expansion of Medicaid it will be interesting to see if the CDC recommendations gradually become more conservative.

I work at a hospital. While employees can not be required to be vaccinated, there is always a big, big push for employees to get vaccinated - and the vaccines are paid for by the company. Makes huge sense from a public health standpoint, since every person who works in a hospital risks exposing the most vulnerable people, our patients, to flu. The hospital also does aggessive outreach with patients, since one patient hospitalized who has or gets influenza risks exposure of other patients, many of whom are in high risk categories.

Although I am generally quite healthy and have been for most of my life, anytime I have gotten influenza it has been much more than "uncomfortable." I don't call "sick as a dog" uncomfortable. And even when I was a child and adolescent, when I did catch the flu, I always ended up with a secondary infection of some sort or another. Of course, when I catch an adenovirus, the common cold to most people, I also get quite ill and am prone to developing secondary infections. I am fortunate in that I rarely become ill, but when I do, I get really ill, even from a cold.

People have a tendency to call many illnesses "the flu" from severe colds to 1-3 day stomach viruses.