Does my daughter need the 2nd swine flu shot?

When I brought my daughter to the Doctor for her 6 month check up last month they gave her the swine flu shot. They told me to call back a month later for the 2nd shot. I called today and they said they are out of them and will not be getting any more in since it is May. I am really frustrated about this. They told me to take her to the health department for the 2nd one. Does she really need to the get 2nd shot? How long can I wait before getting it?