Every year the vaccine manufacturers have just a few months to come up with the
vaccine for the prediction that year.
H1N1 popped up out of nowhere in the early summer. Yes, the testing of this vaccine was rushed, but the process to make it is tried and true.
The swine flu is pretty new to the human species. Apparently it appeared a decade or so ago. So few of us have any resistance to it. Because of this more people will catch it and those that do may have a more severe disease.