The researchers compared the fall wave of the pandemic with the six preceding flu seasons, focusing on the timing of peak activity, geographic spread and community impact.
The pandemic peaked 10.5 weeks earlier than the seasonal flu epidemics, and it spread from west to east in Western Europe, the Centers for Infectious Disease Research & Policy at the University of Minnesota reported.
In addition, the WHO Weekly Epidemiological Record reported vaccine safety advisers reviewed data on the 2009 H1N1 pandemic vaccine and found its overall safety record was reassuring.
U.S. and Canadian studies of the pandemic vaccine in pregnant women were also reassuring, but additional studies in more countries are being conducted.
The researchers noted no new safety signals, other than a previously reported link between the adjuvanted vaccine -- an agent that may stimulate the immune system and increase the response to a vaccine -- and narcolepsy -- a sleep disorder that causes excessive sleepiness -- in children in Finland and Sweden.