The US Food and Drug Administration (FDA) Tuesday approved a swine flu vaccine keeping officials on track to begin a mass vaccination campaign by next month.The Food and Drug Administration has approved applications for vaccine for the 2009 H1N1 virus for four of the (five) manufacturers of the US licensed seasonal influenza vaccine.The US government has purchased 195 million doses of swine flu vaccine and will make shots available free of charge starting next month.The large scale 2009 H1N1 vaccine program will begin mid-October with small amounts of vaccine becoming available the first week of October