[Mrluvaluva]

"It is possible to catch swine flu more than once, but not the same strain, since your body has produced antibodies for the first infection. Flu and cold viruses mutate readily--which is why there is no cure for the cold. If you contract a mutated strain, after already having had swine flu, your body may be able to fight it off easier through 'cross protection', ie. already having dealt with a similar virus."