The FDA approved the 2011-2012 influenza vaccine this week. The strains in this year’s vaccine were recommended by the CDC and the World Healthy Organization after studying virus samples collected from around the world to find the influenza viruses that are the most likely to cause illness during the upcoming flu season. The strains selected for this season are the same as last year: A/California/7/09 (H1N1)-like virus (pandemic H1N1 2009 influenza virus), A/Perth /16/2009 (H3N2)-like virus and B/Brisbane/60/2008-like virus.
People should get immunized against the flu every year- even when there’s no change in the strain from the previous year (like this time). Immunity to influenza viruses declines over time and might be too low to provide protection after a year.