On Monday, the U.S. Food and Drug Administration (FDA) said it had approved the formulation for the 2011-2012 vaccine [1]. This year’s formulation is designed to protect against all three strains included in last years vaccine. Nevertheless, if you received a flu shot last year, you should still get vaccinated again this year: immunity to influenza viruses from vaccination declines over time and may be too low to provide protection after a year.