According to the CDC (last question on the page linked to below), you have to be confirmed with H1N1 by the right type of test in order to make any conclusions about subsequent natural immunity.  This page and other articles at the CDC to recommend seasonal flu vaccinations in the flu target groups and report that there are no special negative effects of being vaccinated after having H1N1.  Specifically, concerning the natural immunity question (pasted from the CDC site):

Will the 2009 H1N1 vaccine be recommended for patients who had influenza-like illness since spring 2009?

All persons in a recommended vaccination target group who did not have 2009 H1N1 virus infection confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR ) should be vaccinated with the 2009 H1N1 vaccine.  However, most people ill with an influenza-like illness (ILI) since this spring have not had testing with the RT-PCR  test, which is the only test that can confirm infection specifically with the 2009 H1N1 virus.  Tests such as rapid antigen detection assays, and diagnoses based on symptoms alone without RT-PCR testing, cannot specifically determine if a person has 2009 H1N1 influenza.  Persons who were not tested, but who became ill after being exposed to a person with lab confirmed 2009 H1N1 influenza should not assume that they also had 2009 H1N1 since many pathogens can cause an ILI, and should get the vaccine if they are in a recommended vaccination target group.

Persons who think they had 2009 H1N1 infection diagnosed by RT-PCR should ask their doctor if they should be vaccinated. Someone who was infected with  the 2009 H1N1 virus and who is not severely immune compromised will likely have some immunity to subsequent infection with 2009 H1N1 virus.  However, vaccination of a person with some existing immunity to the 2009 H1N1 virus will not be harmful and persons who are uncertain about how they were diagnosed should get the 2009 H1N1 vaccine. Additionally, persons recommended for seasonal vaccine should get a seasonal vaccine because infection with the 2009 H1N1 virus does not provide protection against seasonal influenza viruses.