If you have Swine flu once and recover, does that mean you are then immune?

I personally know someone who has Swine flu at the moment and I wondered if her body would now build up an immunity to the virus. She has been really sick but is treating herself at home and taking Tamiflu as the Doc prescribed. Here in the UK the first vaccines will be available to high risk groups next month but will the people who have already had swine flu and recovered still need the vaccine? Is it possible to be unlucky enough to have it more than once or would you be safe once its already been in your system once.