Does the H1N1 vaccine provide lifetime immunity?

How long is the vaccine in your body?
The H1N1/09 vaccine is very quickly absorbed by your body and then it is up to your immune system to take it from there to develop a resistance to the particular strain of flu virus that was in the vaccination and your body will develop the antibodies to protect against future invasions of the same virus. The vaccine was only there long enough to trigger your immune system to begin to work on the immune process.
How long does immunity from a vaccine or having the flu last?
If you are asking, "How long will I remain protected against H1N1/09 from a vaccination or from getting sick with the flu?", then the answer to this is a little more difficult to give.

You will be protected for life against that exactstrain of the H1N1/09 virus that was contained in the vaccine or that you caught which caused you to be ill, and you will likely also have some cross-over protection from very similar strains.

However, viruses do mutate easily, and if later you are infected with another strain or mutation of the H1N1 virus, and if your immune system does not recognize it any longer because it has mutated to a different form, then you may have no immunity to that new strain. This is one reason we need to take annual vaccines for the rapidly mutating common seasonal flu strains.

See the related links section below for a link to an article on the Time/CNN Health and Science web site about this subject. Here is an excerpt from that article:

It turns out, however, that those antibodies [developed from a flu vaccine or from having the flu] - unlike those against illnesses like tetanus or whooping cough - can provide a formidable and life-long defense against the flu, as long as they're pitted against the correct strain. For an explanation, TIME asks Eric Altschuler, assistant professor of physical medicine and rehabilitation at the University of Medicine and Dentistry of New Jersey, and co-author of a recent paper in Nature about antibodies to the 1918 pandemic flu virus.

Q: How long do flu antibodies last?

A: According to our study, it appears they can last the entire lifespan of the human organism - 90 years plus...

More:
It's important to keep a record of vaccinations so the doctor knows when your child is due for a booster. Also make sure your child gets the seasonal flu vaccine each year. Having been immunized last year probably won't protect someone from getting the flu this year because flu viruses constantly change. That's why the vaccine is updated each year to include the most current common strains of the virus.

The flu vaccine reduces the average person's chances of catching the flu by up to 80% during the season. But because the flu vaccine doesn't prevent infection by all of the viruses that can cause flu-like symptoms, getting the vaccine isn't a guarantee that someone won't get sick during the flu season.