How long does it take for the H1N1 vaccination to take effect?

Getting the H1N1 vaccine doesn't equal instant protection against the virus.

Children under 10 need to have two vaccinations - approximately one month apart - to achieve the proper immune response. Within approximately two weeks of the second dose, they should be protected in the vast majority of cases.

Adults (who only need a single dose of the vaccine, since their bodies already have a mature immune system that is practiced at protecting the body this way) should be protected in 8-10 days after the vaccination.

The delay time between vaccination and immunity is required for your body to analyze the vaccine and produce an immune response, which includes the development of the proper pattern of antibodies that will be effective against that strain of virus. Once the pattern is "known" by the immune system, these cells can be quickly produced to attack any of that strain of virus that enters your body after the immunity has been developed. The antibodies will prevent the virus from being able to make you sick.