No effect of 2008/09 seasonal influenza vaccination on the risk of pandemic H1N1 2009 influenza infection in England.

This study reports effectiveness of trivalent influenza vaccine (TIV) against confirmed pandemic influenza infection in England using a retrospective test-negative case-control study. Cases and controls were frequency matched by age, swabbing-week and region. On univariable and multivariable analysis adjusted for underlying clinical risk factors, cases were no more or less likely than controls to be vaccinated with 2008-09 or 2007-08 season TIV.