Originally Posted by Libertine

And that's why a vaccine with, say, radically new and different adjuvants would have to be tested extensively before being used. That's the whole point here, which has been described rather thoroughly in this thread: this H1N1 vaccine is not something radically new. It uses well-tested adjuvants, and the only really new part is the strain of influenza that's present in an attenuated form. But if the attenuated form of the virus would have serious long term side effects, the same would go for the actual virus a thousandfold. Not to mention the fact that those side effects would also have showed up using attenuated forms of similar strains over the past decades.