Flu vaccine associated with increased H1N1 influenza incidence

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Assessing the impact of confounding (measured and unmeasured) in a

case–control study to examine the increased risk of pandemic A/H1N1

associated with receipt of the 2008–9 seasonal influenza vaccine

Vaccine (in press)

http://www.sciencedirect.com/science/article/pii/S0264410X11015891