All flu doesn't behave the same way.
Each flu attacks differently, within a limited set of parameters.
Each flu has a different set of symptoms. Some are more dangerous, some are less dangerous.
Not each flu is dangerous to the same population. Flu is not always dangerous to people at all. Some flu is simply dangerous to ducks, which is why China is one of the big sources for flu. They raise and consume a huge number of ducks. This is why chicken eggs are often used to create the vaccine, because of the easy availability over here and because flu loves birds.
When flu crosses over the line and infects people, each variety of flu finds different sorts of people more tasty. Some kinds of flu love old folks, because their immune systems aren't very good. This is not necessarily so good for the flu itself, because when it kills its host, it kills itself as well. A lot of the structures inside your cells were once, we think, diseases that our bodies adapted to and reached a compromise with, good for our bodies and good for the illness as well. The illness gets to survive as part of a larger structure much more successfully than it could have ever done on its own. The body has made friends with an enemy, and now has a useful structure to, for example, do cell repairs.
Flu is trying to reach a compromise with birds or people or pigs to make it more successful as an organism. If it succeeds, it's good for everyone. If it fails, it may kill us off or kill itself off. It's trying a whole range of different ways of doing this very rapidly. We have vaccines against at least three different strains of flu every year, but there are many more of them. The H1N1 is not one of the three included in the usual three flu package shot this year. I am not clear why that is.
The fact that it is being distributed differently, however, offers a clue. The regular flu shot apparently goes after the usual people in the usual way. So, in order to give it, they can all be bundled together in one injection and reach everybody who needs that shot, including you and me. We are the people that the regular three flu bugs of the year find tasty. We are the usual suspects, as they said in Casablanca.
The H1N1 flu appears to be a different character. He doesn't find the usual suspects as tasty. If he took a bite out of you or me, he'd probably be likely to make a sour face and say pfui. Then he'd spit us out as not being to his taste because what H1N1 wants is an experiment. He wants to try the taste of other human folks who taste different than us and might give him a chance to survive longer and get a bit further down the line toward organelle status. So he's trying a different evolutionary strategy. It's important that if we're going to block that move, that we should target those people that he's going to find tasty. You and me are not very high on his menu list, which is why we got special treatment for the regular flu shots, where we are high on the tasty dish list. For H1N1, the order of tastiness appears to have been flipped.
Near as I can tell that's the deal.
Sincerely, Bob Kaven