How long does it take for the h1n1 vaccine to work?

Not a separate vacci. H1N1 is not a separate vaccine but is incorporated in the annual flu vaccine.It start working right away.But according to CDC it takes 2weeks to get full immunity.
10 dats. The latest data shows that a good immune response develops within about 10 days of receiving the vaccination. But for children under 10, they don't develop a strong immunity with just one dose. That's why they need to get a second vaccination within a month of the first one.
About 2 weeks. After a person receives a flu vaccine, his body starts to identify the virus (if live vaccine) or pieces of virus (if non-live vaccine) as foreign. Then his immune system, with its white blood cells, lymph nodes, and spleen, remembers the virus's parts and makes antibodies against them. In about 2 weeks, his body should be able to recognize and destroy the 3 flu virus types in the annual vaccine.