Mid-season influenza vaccine effectiveness 2011-2012: A Department of Defense Global, Laboratory-based, Influenza Surveillance System case-control study estimate

► We estimate influenza vaccine effectiveness using cases and test-negative controls. ► This is the first midseason U.S. VE estimate for the 2011-2012 influenza season. ► Influenza vaccine appears to offer moderate/high protection against influenza. ► Adjusted estimates were similar between trivalent and live attenuated vaccines. ► This program is positioned to estimate midseason VE annually and during pandemics.