When H1N1 was frequently on my mind last fall, my reading turned up elderberries as a tool against influenza, at least seasonal influenza, but I don't see why it wouldn't have some effect with H1N1.
Arney, current research on elderberry extract definitely shows it helps the immune system fight off viral infections such as the flu. It's a multi-mode system, one part of which is to stimulate the cytokine production. Unfortunately, this is also the effect of swine flu, namely triggering a cytokine storm which can be even more devestating/fatal to the infected person. Cytokine storms were one of things which made the original Spanish flu to deadly, especially for young, healthy people.
The scientific community has not formally studied this issue, but after looking at the assorted data that has been done I personally would not take an elderberry extract if I thought I might have swine flu, and this is from a guy who still drinks from BPA-containing nalgene bottles.
-Blast
Ref. 1:
Elderberry Flu Protection Ref. 2:
Cytokine Storms Ref. 3:
Elderberry Cytokine Storm?