As far as i know you are immune for some time after you had it. but then again i guess you are only immune for the exact virus strain you had. and since its a given fact that the virus mutates you can easy get it again.
See my 25. This little boy was tested both times by his specialist at UCLA, for H1N1, the expensive test, because he has other health issues.
He really did get H1N1 twice. Who knows, maybe it was a different mutation because it was 4 months between getting it. This beautiful little boy got through it even with compromised lungs, two times. He’s fine.